(Set after the war with Gaea, married life)
Also my own little creation.

Percy Jackson was half awake, but even in his delirious stage, he knew it was his birthday. Suddenly he sprang up like a little kid at a candy store and smiled wildly at Annabeth.
Only, Annabeth wasn't there, which puzzled Percy. Still confused, he slipped on his clothes and exited the room.
"Annabeth?" He called. A muffled answer replied. Percy's muscles relaxed and he hadn't even realized they'd tensed.
He entered the living room to see Annabeth seated on the couch. The war with Gaea had ended years ago and Annabeth and he each attended the same high school and college. After college they had gotten married, and, thanks to the gods' generosity for saving the world several times, had bought them the house Annabeth had designed especially for them, with a pool and everything. The gods had even covered the wedding expenses, mostly Aphrodite, because, according to her, they were her "OTP".
Percy smiled, "guess what today is?"
Annabeth put on a mock thinking face. "Hmm, August 18th? I don't know."
Percy sat next to her on the couch.
"Happy birthday, Seaweed Brain." She shoved a box in his face.
"What's this?" Percy asked. Annabeth smiled. "Your gift, any more stupid questions?"
For once, not this time. He tore the wrapping paper open, in his peripheral vision he saw Annabeth biting her lip. He opened the box and gasped.
"How did you know. . ." He asked in awe as he pulled out his new panda pillow pet.
"I asked around for a good gift, and Reyna mentioned something about a pillow pet." she replied.
Percy laughed. "This is exactly what I wanted, Wise Girl."
"I'm glad," Annabeth whispered and leaned in, their lips colliding.
They were kissing for a while when all of the sudden there was an explosion outside coming from their backyard.
"Leo." They said in unision and ran outside to find out what it was this time. This had been the second year of marriage, but it had already become tradition that Leo and the rest of the seven, Nico and Reyna included, invade for every special event.
What was in their backyard were the remains of a rocket. They looked up to see a scrawny, curly haired boy floating down from a parachute. Annabeth walked up to him.
"LEO VALDEZ IS HERE!" Leo screeched as he fell to the ground. A girl with a caramel braid fell behind, also attached to a parachute. Leo stood on the ground, followed by the girl. "And . . . Calypso," Leo announced with less bravado. That earned him a playful punch from Calypso.
"Now it's a party." Percy smirked. Leo smiled, "what, you were planning on celebrating without Uncle Leo?" He joked.
"Where's Piper and the others?" Annabeth asked changing the topic. Leo smirked and picked up a piece of the rubble.
"Ah, they were wimps, especially that Beauty Queen. 'You're crazy Leo', 'it'll crash Leo', and was she right? Yes!" He grinned like a maniac.
"Oh and happy birthday, Percy. Calypso, do you have the present?"
Calypso shrugged. "Well in the time it took to evacuate, I was able to grab the present, risking my life, of course." She glared at Leo. He didn't seem to mind. Annabeth ushered them inside the house. Percy, impatient as always, demanded for his present.
Calypso handed it to him. He opened the present. When he saw what it was, he glared at Leo. He had a new projection of Coach Hedge, like the one on Buford the table.
"PUT SOME CLOTHES ON!" The projection screeched.
"Dude, that things gonna be screaming at me every time I shower."
Leo shrugged in response and was about to say something when the door blasted open.
Jason, Piper, Hazel, Nico, and Reyna were greeted by Percy's new projection screaming for twenty push ups.
"Leo, that's genius." Jason said nodding his head to the projection.
"See! See, Frank, Jason admits it! Wait, where's Frank?"
"He'll be here later." Hazel said. Percy found that strange, but didn't question it. Everyone walked in and Annabeth walked over to the door which was now on the ground in pieces.
"Again?!" She demanded angrily. He walked over her and pulled her into a hug, "hey, Annabeth, they do this every year. No biggie."
She looked ready to argue but decided against it.
Leo ran up to the door. "Never fear! Leo McShizzle Valdez is here!" He set to work on the broken door. The others took a seat on the couch.
Each person wished Percy a happy birthday with a hug or a pat on the back, except for Nico.
"We've been over this," Nico said warily, "I don't care if it's your birthday, I don't like hugs."
Percy eventually gave up and sat back down.
"So, Percy, any plans for today?" Reyna asked.
Percy did in fact have plans, and after putting up with everyone's grumbling and complaining, they sat to watch Finding Nemo.
Percy was ecstatic during the whole film, quoting it and everything. He even tried to communicate with Nemo, sadly, it didn't work. Every now and then, Annabeth left his side, looking a little pale, but she insisted it was nothing to worry about.
Percy motioned to Jason.
"Okay Bro, give me the gift." Jason turned pleadingly to Piper. Percy understood immediately, his Seaweed Brain able to comprehend the silent conversation the couple was having. "Jason, you forgot to buy me something?" Jason shifted uncomfortably.
Piper handed Percy a bag that said: Happy Birthday!
"From both of us," Piper said, sending Jason a you-owe-me look. Percy nodded and opened the bag to find a stuffed Pegasus inside.
"This is awesome!" He said holding his new toy, "thanks Piper, and uh, Jason."
Annabeth took a picture of Percy with his stuffed animal, claiming he looked adorable.
Percy was about to open his present from Hazel when Annabeth had announced that the cake was ready. Percy wasn't even aware that she had baked a cake for him, but then again, he was an oblivious Seaweed Brain.
They made their way to the large dining room. Annabeth had done an outstanding job designing the house, and Percy knew that Annabeth knew that their friends would come often, so they had two dining rooms. One was much smaller, with just enough room for a table and some chairs, while the other dining room had enough space to fill two living rooms.
Annabeth came out carrying the cake. The inside was vanilla with blue food coloring and the outer layer was coated in a dark blue frosting.
She set it right in front of Percy and sat right next to him.
They were about to start when they heard a loud crash coming from the living room. Annabeth sighed in frusteration. Percy noticed that she seemed more irritable lately. Once he asked about her day and she exploded, screaming about how horrible her day had been.
"Good news," Nico said, "I don't sense any deaths." He winced. "Well, maybe the death of a few vases."
Percy heard another crash and then an elated, "BROTHER!"
Percy lighted up. "Tyson!"
Tyson came up to Percy and held him with his huge arms, crushing Percy's ribs.
"Can't . . . breathe . . ." He managed tapping the big guy's arm. Tyson got the hint and let go. Percy inhaled, grateful for air.
Behind Tyson, Grover followed.
"Hey Goat boy!" Annabeth said giving Grover a hug.
"Couldn't miss Percy's birthday." He said.
Finally, everyone (except Nico) began singing Happy birthday to Percy.
Before he blew the candle he prayed silently for a happy year with Annabeth and his other friends.
Percy blew out the candle and everyone (except Nico) cheered.
Percy began cutting the cake and passing pieces to everyone. Apperantly, he was slow at cutting cake because Leo yelled, "Come on, Water boy! Go faster, I'm hungry." Only because Leo called him 'water boy', Percy gave him his piece last.
They all ate and laughed and told stories about their adventures together. Everything was perfect. Percy went on and on about how awesome Finding Nemo was while everyone else tuned him out. Annabeth ate more than Percy had ever seen her eat. She was on her fifth piece of cake when Percy asked if she was full.
"Not at all," she replied and went back to eating.
After everyone was done picking at their cake, more presents were exchanged.
Percy demanded for Hazel's first. The gift, whatever it was, was hidden inside a large bag and heavy.
An overjoyed Percy pulled out the gift.
"Hazel!" He yelled, "It's Nemo!"
Hazel didn't feel like crushing his happiness by telling him that it was a goldfish and not a clownfish.
Percy was son of the sea god, and did in fact know that it was a goldfish, but still insisted on calling him Nemo. That was, until 'Nemo' transformed into Frank.
Percy was so surprised he dropped the fishbowl while everyone, including Nico, was laughing.
"Cheapskate," Leo yelled at Frank.
"It's called being creative, Leo," Hazel said.
"Same thing!"
"Okay, break it up, Ladies!" Percy called, "I just want my gifts!" He scanned the croud and pointed at Nico.
"Nico. Gift. Now." Nico shrugged and pulled out a small item taped hastily together. He tossed it to Percy.
Percy opened it looking appaled. "Have I ever told you you're evil?"
Nico smirked, "being a son of Hades, I get that a lot."
"What is it?" Reyna asked.
Percy blushed. "I'd rather not."
"Please?" Calypso asked.
Percy sighed and held up a bracelet. It looked cheaply made, and on it were the words I'm still not your type. Stop dreaming.
They passed the bracelet around. Annabeth was the only one who got it and started cracking up. She and Nico high fived.
Percy groaned. "Next, Tyson and Grover."
They had explained earlier during cake that they were both low on Drachmas and put their money together to purchase something.
Percy's eyes tripled their usual size as he scanned the bag.
"What is it?" Frank asked sounding a bit agitated that he was taking forever to reveal his gift.
Percy held it up. "It's the real Nemo!" He scowled a little at Frank and Tyson gave Percy another bear hug. Percy thanked both Tyson and Grover and they returned to their spots.
Percy was infatuated with his stuffed Nemo and kept muttering 'Just keep swimming'. Everyone at the table facepalmed, including Annabeth.
Reyna tossed her gift to Percy. Inside, he found a huge bottle of blue food coloring.
He smiled widely at Reyna and thanked her.
Percy wanted to watch Finding Nemo yet again with his new plush Nemo, but Piper was able to charmspeak him out of it. Instead, the remainder of his birthday was spent swimming.
The girls for the most part relaxed in the sun.
Percy and Jason had a few competitions to see who was more powerful. Percy won each time. No surprise there. Jason claimed that he was going easy because it was Percy's birthday, but they both knew that wasn't true.
Frank kept turning into a fish and Percy and he were able to communicate and come up with plans to aggravate Leo and Jason. Jason was easy to annoy, however, there was no annoying Leo. In fact, Leo ended up aggravating all of them.
About two hours later, the other girls jumped into the pool.
Tyson, Grover, Reyna, and Nico left early leaving the Seven to swim. Percy created tsunamis for the others and shielded Annabeth away from the mini storm. Even so, she seemed sick and would leave the pool to rest every now and then.
Percy led Annabeth underwater, and created an air bubble. To keep the others away, he created a mini storm above. Percy and Annabeth's annual underwater kiss was as amazing as usual.
Sadly, Percy's day eventually ended. His friends left. Piper and Jason were bickering about who would drive. Hazel and Frank were laughing together while Leo and Calypso tried to figure out a way to get back.
Percy and Annabeth stood aside watching Leo work while Calypso stood pointing out his mistakes.
In a few minutes, Leo had constructed a helicopter-like structure.
"The last time you made a helicopter, it destroyed my dining table." Calypso pointed out warily.
Leo grinned. "It's safer," he kicked it and surprisingly it stayed intact. "The only reason it malfunctioned was because I was in the air, falling to my almost death, and this baby saved me!"
"Wow, Leo. 'Malfunctioned', that's a big word." Annabeth teased.
"Shut up, Annabeth!" They set off in the air and Percy and Annabeth waved goodbye.
"HAPPY BIRTHDAY PERCY!" Leo and Calypso screamed in the air as they flew off.
Annabeth turned to Percy.
"Well, that was fun."
Percy nodded in agreement.
Annabeth bit her lip. "Seaweed Brain, I have something to tell you." Percy noticed that she looked nervous.
"Okay." He followed behind her to their living room and he sat down.
"Are you okay, Wise Girl?" He asked. His voice was full of concern.
"Percy," she whispered, "I'm pregnant."
Percy stared in awe at her. Finally the pieces fit in, he couldn't believe he didn't notice before.
He looked at her stomach expecting something to be there, but it looked about the same size. He looked back at her and hugged her.
"This is amazing," he whispered to her still in awe. "This is . . ."
He couldn't even form the rest of the sentance. Words could not describe the emotions that washed over him. Annabeth was pregnant. He would be a father to an unknown child.
It was the best birthday present he'd ever received.
"PUT SOME CLOTHES ON!" The Coach Hedge projection screamed. Percy and Annabeth started laughing. The fact that the Coach had interupted their moment made it seem all the more memorable.

Happy birthday, Percy!!! What have you all done to celebrate?
I'm wearing blue, the words 'Seaweed brain' are written on my wrist and I'm carrying around a ballpoint pen. Later I'm gonna make blue cookies (well kind of, the store did not have blue food coloring I looked everywhere! So icing) And I'm gonna spend the rest of the day rereading my favorite PJO parts. And I've been writing this. I'm sorry if it was bad. Sorry.
Go celebrate Percy Jackson's day!!! Ily!