Autobots

Optimus
He would leave a sweet and simple letter with a poem or two with a heart-shaped chocolate box. He isn't all that into being very extravagant and overkill on things, so don't expect any giant stuffed bears or huge bouquets of flowers on Valentine's Day. He would be grateful if you were to get him something. Just be sure to do everything anywhere but public, because he knows that Miko won't let him live it down for the rest of his life. He has taken a liking to Earth candies through, so be sure to surprise him with chocolates and any other sweet you can get! Optimus would take you to a small lake with a picnic set up. When night falls, the two of you would stargaze as he explained Cybertron, the astronomy of his home planet, and if he feels close enough to you, might even open up about his past relationship with Megatron, formerly Megatronous.

Ultra Magnus
Don't ever expect much of anything from this mech. At best, you'd get a flower or two with a small box of chocolate. At worst you'd get a simple Valentines Day letter. He would be incredibly flustered if you were to get him something though. Magnus was never, and never will be, the mushy, all romantic type. He would most likely take you somewhere on a cliff to watch the sunset and share a few candies. If you're lucky, he might even build up the courage to confess his feeling to you.

Ratchet
He's a downright stickler for Valentines Day. Well, the end of it at least. Ratchet acts like the day is like any other day, and ignores all the nonsense the other children pull. Near the end of the day, when you're near tears because you had thought he had forgotten, he would give you a small box of the conversation heart candy and possibly a small bracelet. He would try and fail horribly to act chill and brush off any gifts that you get him. He has a secret love for Earth poetry, so expect to get a poem or two throughout the day from him. He would put in a sappy romance movie, such as Titanic or Twilight.

Bumblebee
Bumblebee would be over the top for everything. He would try to get you the finest things he can for Valentines Day. Expect a LOT of red roses, love letters, chocolates, lovey-dovey stuff, and confessions.   He would bounce in happiness if you were to get him something for himself. He would beep and buzz to make sure you knew that he was grateful for your effort. His first tactic would most likely be to leave a romantic letter with a poem and a few chocolates on a table that says to meet him somewhere at a certain time. If all else fails, he will literally swoop you off your feet and take you to the destined location where he would confess his true feelings to you and spend the rest of the night hugging and watching stars.

Bulkhead
Bulkhead is pretty iffy. He wouldn't know what to do, so he'd look up what most humans do, leading him to leave a love poem and a white rose(because he thinks red roses are just a little to right-out-of-the-book). He would be completely blown away should you get him anything of his own. He would take you to a beach where you would watch the sunset and he would talk about what life was like as a wrecker on Cybertron.

Wheeljack
No questions asked, a flight on the Jackhammer would be in store for you. During the previous day, he would spend hours upon hours of detailing tiny chocolates that he made himself because he doesn't trust store bought goods to be good enough for you. He would not be afraid to show, unlike pretty much everyone else, how he felt about whatever you got him, no matter how big or how small. He would make a few questionable jokes here and there, but aside from that, the two of you would just hang around the Jackhammer the whole day while going sightseeing where ever you wanted to go. He absolutely adores flowers form Earth, so if you really want to wriggle your way into his spark, be sure to get him some 'Morning Glories' or a handful of 'Forget Me Not's.

Smokescreen
He is a Jack-in-a-Box rigged to go off the very astrosecond you enter base. He would have only the finest of the fine, the best of the best for you. He would get you whatever you wanted, no matter how pricey it was (poor Fowler's bank account, dried up like a riverbed in the Gobi Desert). He would take you out to a stunning forest scene to eat dinner. From there on out, he would spoil you with jewelry, flowers, and kisses. He would outright admit his feelings for you, in hopes that you would do the same for him. He would be jumping for joy if you got him anything. Whatever it is that you got him is sure to be treasured forever. You would most likely be explaining to your parents why you came home so late the next day. You said "hanging with friends" when really, you were enjoying the night sky with Smokescreen. He loves animals to no end, so be sure to remember to take him to a petting zoo or something of the sort.

Cliffjumper
He would be pretty chill throughout the day, giving a rose here or there, maybe stumbling across a box of candies, all while hinting at something bigger being ready for that night. Do not ever underestimate him, because while the little 'treasure hunt' seemed sweet and simple, he has an entire organization going on to make the night absolutely perfect. He would be pretty bummed should something go wrong, but would keep in happy spirits for you. The two of you would spend the evening dinning at a two-person table at a little outcropping in Italy.  To impress you, he may even attempt to do an Italian accent, or juggle some random things he found. He would be incredibly happy if you got him something on Valentines Day. If you wanted to spend some more time together, you could always get him to talk about ancient civilization on Cybertron. Turns out that the history of their planet wasn't to different from Earth's.

Arcee
She would keep it concise and to the point. She wouldn't have anything planned out, so long as she got to spend time with you. She would talk passionately about the Valentines Days on Earth she would share with Cliffjunper and her happiest days with Tailgate. If you are fortunate enough, she will openly express her true feelings, which is rather a sight to behold as she rarely does that. She loves white chocolate, so be sure to get her some. If you were to get anything for her, she would brush it off but be internally grateful that someone cared. The two of you would watch the sunset over a jungle as she talked about the good ol' days back on Cybertron.

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Let me know what you guys think! Should I do one on the Decepticons and One interception the humans? Or just one or the other? The feedback is helpful. I hope you all had a very happy Valentines Day!

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The Humans

Jack
Despite his normally calm, totally chill demeanor, he despises classic and tradition. He only plays along so he won't stand out. So, you would probably get some rainbow-colored flowers, a small note, and a K.O. Burgers gift card. He would be very grateful if you were to give him something. His idea of a nice night would be binge watching something on Netflix with ice cream.

Miko
She would do whatever it takes to make sure that you have the best day ever. If it meant stealing Ratchet's wrench and using it to bribe him into groundbridging the two of you wherever your heart desires, then so be it. She would drag you off to as many monster truck rallies as she can before Bulkhead finally says that they've been to enough for the day. She would be ecstatic if you have her a gift. Expect no flowers, no love notes, no poems, and only chocolates.

Raf
He's Miko with a twist. Your chocolate box would actually be a lightweight metal heart-shaped box programmed to chill the sugary substance inside in order to prevent them from melting. Poems and letters would be a bit over-the-top in his eyes, so he would most likely ask Bumblebee to take you both on a drive. If it come to be a 'come-to-the-lord' moment, the little sucker will ask Ratchet to bridge them somewhere. He would be super exited if you were to give him something. If you gave him chocolates, he would be bouncing the whole night. If you gave him a picture of him and Bumblebee together, he would be superglued to your hip for the rest of the day.

Decepticons

Megatron
It would fly over his helm like any other human holiday. He wouldn't bat an optic as to so much as to looking into it. If you were to become depressed and sad over it though, you might hit the jackpot and get a few chocolates followed by a flower. If you were lucky enough to wriggle into his spark, he would do the complete opposite. He would be an absolute gentlemech, treating you like the most important being in his life. And you were (aside from Orion Pax). You would be bombarded by sweet little nothings the whole day, and would enter your room to find an enormous pile of chocolate boxes in it. On top of that, he may even get you some simple jewelry, such as a necklace or a few sets of earrings. He would slowly accept any gifts you got him, saying thing like "You shouldn't have." If you are lucky enough, he might open up to his past of being Megatronous and his days with Orion Pax.

Starscream
Important to him or not, he'd ignore the holiday, saying that he has a reputation to uphold. Don't be surprised to find a small assortment of chocolates on your bed though.

Soundwave
He would look up every possible move for Valentines Day before actually doing something. He would most likely send Lazerbeak out to fetch and bring you to the top of the Nemesis, where you would eat energon sweets and candy. After a while, the two of you would slow dance to some waltz music that Lazerbeak would play. He would show you all of the constellations in Earth's sky and even do his best to point to where Cybertron was. He would end the night by transforming, activating his holoform (courtesy of Knockout) and giving you a kiss on the lips, leaving you questioning life itself while Lazerbeak recorded the entire ordeal.

Dreadwing & Skyquake
The twins would follow you around like lost puppies, doing whatever you want and helping wherever possible. Skyquake would get you something along the lines of your favorite gaming series and a small TV to hook up to the Nemesis, while Dreadwing would bring in a tiny cake he made
(which surprisingly turned out pretty dang good. How does he even make it with those huge servos? Oh wait- holoforms) and the entire collection of your favorite book series. The two of them even took the time to learn how to play video games in their holoforms in order to spend more time with you. At the end of the day, you will probably be sitting in between their holoforms in the couch while having a movie marathon of The Hunger Games while eating popcorn. If lucky enough, they will share their feelings towards you. Your chances of being able to give them anything more than a great day is low, so they would be grateful and somewhat shocked if you got them something. And as it turns out, Dreadwing and Skyquake have a huge weakness for puppy dog eyes and toffee.

Knockout
He's a pervert. That's all that needs to be said. He would act all innocent and adorable in hopes of falling into his trap. Clearly, since this is being recorded, his plan failed, so he settled with cuddles and chocolates. If you try hard enough, you can persuade him to learn to play on the Wii with you. You would fall asleep next to him on the couch surrounded by blankets, pillows, ice cream, popcorn, and candies galore. He would feel guilty though if you were to feel sick the next day.

Breakdown
The big and tough Decepticon act was really just a cover up for the big sweets park of a softie the mech is. In the morning, you would find a love note and a few chocolates on your bed stand. He would take you out to see world wonders throughout the day, using the groundbridge to teleport from place to place, wether it be to Rome, Italy or to the ruins of Mesopotamia,  he would take you literally anywhere and everywhere. Along the way, he would buy you little trinkets here and there. It would mean the world to him if you gave him something. You would spend the night in Athens, Greece to watch the stars and the Moon. For being an alien, he is extremely curious about space and what lies in it. At night, he would read you some bedtime stories to help you fall asleep.

Arachnid
She would poison your chocolates and watch you cripple and wither in pain inside of your cage while cackling like a madwoman the entire time.

Hardshell
He would be very straightforward about his feelings, and hope that you return them. He would take you out for a walk in an abandon energon mine to just talk about life and things in general. Mostly about Starscream's biggest fails ever though. He would somehow convince one of the vehicons to get a small box of chocolate for him so he can give it to you at the end of the day. He would constantly rub you with his mandibles to remind himself that you're still there.

Shockwave
The holiday would seem illogical to him, so he wouldn't do anything about it except putting a box of chocolates in your tank to see how you react. He would glitch out and fall over if you were to get him anything.

Makeshift
Good job to you if you can convince him to even come close to considering human tradition! He would get you a bouquet of flowers, but no chocolates because he doesn't want you to get sick from eating too much sugar. He would take you to the top of the Nemesis so the two of you could enjoy the view of Earth. His spark would melt if you were to get him something on Valentines Day. When he tucks you up for the night, he may even recite a love poem he wrote himself for you.