This is a 3+1 thing.
3 times the team saw Robin use acrobatics and the 1 time he showed them. 

It is still set in season 1.

Hope you enjoy.

Robyn out.

1

The first time the team saw Robin use acrobatics was on a mission.

It was supposed to be a covert mission (as most of their missions were supposed to be). A simple sneak in, do surveillance to get information and sneak back out. Of course it went wrong almost immediately and the villains (who couldn't really be officially called villains - they only had some half baked plan that would never work) were alerted to their presence. On this occasion (like many) it was due to Kid Flash and Artemis getting into an argument which escalated from their mental link to full out shouting.

It quickly lead to them fighting the group of extreme eco geeks, who were just a bit over the top (meaning they wanted to destroy half the human race, claiming less people meant less pollution - it would never work but it was easier to stop the nonsense now before it got any worse). The team had abandoned their hiding places around the warehouse they were in, brawling in the main hall. They weren't doing too badly despite being greatly out numbered, which of course is when things went downhill. More thugs entered the room and the team were soon surrounded by a group of well armed thugs. The fighting paused, both sides playing a game of chicken to see who would move first. To everyone's surprise Robin was the first to move - launching himself up off of Superboy who launched him up into the rafters on reflex, and disappearing from view. Thankfully it had distracted the thugs surrounding them and allowing them to leap back into action.

The team expected Robin to try and climb down carefully and re-join the fight, but to their continued surprise Robin had instead gracefully leapt across the rafters until he was on top of the largest group of thugs. With a double flip he landed on one of the thugs who had been about to shoot Artemis (she had been facing the other direction, offering cover to Aqualad) with some unknown weapon.

The acrobatics continued throughout the fight. Any time a team member glanced his way he was in the midst of some acrobatic feet - a flip here, a cartwheel there and even the occasional back flip. Even Wally who knew who Robin was and seen him use acrobatics before, was shocked at how graceful his friend was even in the midst of a fight, incorporating his acrobatics into his fighting style with ease. So it was no surprise that after all the thugs were knocked out and they had retrieved the information needed (mostly on the unknown weapons), that the team surrounded Robin and started firing off questions rapidly.

"How did you do that -?"

"What was that-?"

"Can you show me how to -?"

"Growl-?"

Aqualad, being the rational and mature one, silenced his teammates and asked calmly. "How did you preform those tricks my friend?"

But the only answer the team received was. "An old family secret." Leaving the team even more confused than before, at least they had gotten the info they were sent for.

2

The second time the team saw their youngest member's acrobatic skills, was back in Mount Justice.

The whole team was relaxing after a (rare successful) mission. Everyone was in their civilian clothing and enjoying the down time. M'gann was cooking cookies (and burning said cookies), Conner was attacking a punching bag (imagining it was the Blue Boy Scout himself, Superman), Artemis and Wally were arguing (about whether ornithophobia was a real fear. Wally said it was, he claimed to have it, and Artemis denied it was a real thing and that he had it), Kaldur was attempting to read a book (and failing) while being in two metres of the arguing love birds, well archer and speedster (the book had something to do with wizards on a glance at the front cover, beginning with a P) and Robin was no where to be seen.

"Hey where's Robin?" Wally questioned, getting bored of arguing with Artemis.

Everyone looked up at the question but nobody (HeHe nobody-oops wrong fiction) had an answer. They had heard him enter the cave and had seen him before he disappeared about an hour or so ago.

"How about we go look for him. Then maybe we can do some team building?" Suggested Aqualad always the calm mature one. Everyone nodded and agreed to start looking, splitting up to search the base. They searched for about half an hour before giving up and collapsing on a couch/chair in the main sitting room.

"Wait, I think I can hear his heart beats coming from the training room." Conner sat up, concentrating.

"Why didn't you do that before?" Wally whined.

Conner shrugged in response, then started walking towards the training area, everyone else trailing behind. They followed him all the way to the entrance of one of the smaller training rooms, the door had been left slightly open - allowing them to see all the gymnastic equipment. It was a smaller training room that was rarely used by the majority of the team; mainly due to it being filled with gymnastic equipment and trapeze equipment. They barely entered the room before spotting the missing team member - he was swinging on parallel bars doing intricate tricks often featured in the Olympics.

They watched entranced as he did series of swings and flips, moving elegantly between the bars and continuing to do tricks with practised ease, then he transferred gracefully to the balance beam. Robin was an incredibly skilled acrobat but arguably the most amazing thing was that like the others he was in civilian clothes and wearing his feature sunglasses - no one had an idea how they were staying on. He didn't seem to notice them and silently glancing at each other they tried to back out of the room.

They were stopped in their tracks by Robin shouting from the midst of a cartwheel along the balance beam. "Ornithophobia is real, it's the fear of birds! But Wally is scared of ducks specifically!"

"You're afraid of ducks!?"

3

The third time the team saw Robin doing acrobatics was in Happy Harbour. The team had been enjoying a free day in town, they had been to the cinema for a 'teambuilding exercise' (that was how they justified it to Batman and managed to secure the free day), and to introduce Conner, M'gann and Kaldur to more Earth and land culture.

Nothing had happened when they were at the cinema, in fact they all had a nice time watching a movie, eating popcorn and other cinema treats. They had all enjoyed 'How to Train Your Dragons' (it had been part of the agreement that they saw something age appropriate for all of them).

It was after the movie that things went wrong. Because things always went wrong with them, it was inevitable. They had been strolling back to the mountain, chatting away (Wally and Artemis weren't even arguing), when a scream caught their attention. Ever the heroes, they all rushed to see what was wrong with a single glance. They followed as Conner lead the way to the source of the noise, ending up at the entrance of a dirty back alley. Down the alley they found a teenage girl, no older than 15, being mugged with a guy with a knife. She had stopped screaming, just whispering as she tried to avoid the knife she was being threatened with.

It took them a second to react but it was a second too late. Robin, still in civilian clothes and wearing his signature sunglasses, dived or more accurately flipped into action. He seemed to do some kind of dance with the man, half way through a cartwheel he kicked the knife out of his hand and leapt into a flurry of punches, knocking the mugger out. Artemis pulled the girl out of the way, comforting her as she started to cry as Wally pulled out his phone to call the police.

No one questioned Robin's acrobatic moves, they were way too used to it by now and accepted it as part of the Boy Wonder's fighting style. He used it in most of the fights they had gotten into. At least the situation hadn't delved into uncontrollable chaos as many of their missions did.

+1

The team were back in the cave again, relaxing on a hot summers day. They had given up trying to do anything as it was far too hot, deciding that lying around and enjoying the air conditioning was the best use of their time. The only person missing was Robin who, according to Wally, was using his 'freaky ninja skills' to disappear. As if by magic, said 'freaky ninja' appeared from down the corridors with a giant grin on his face.

"I have something to show you, follow me!" Robin than bounced away, back down the corridor towards the training rooms. After getting over the initial shock of him appearing (and the energy he had - it was far too hot for actual movement), everyone leapt up and shuffled after the Boy Wonder. They were led back to the training room full of gymnastic/trapeze equipment and herded into the room with a perfect view of the trapeze.

Robin grinned at their confused faces and sprinted up to the trapeze. Wally smirked guessing what Robin was going to do and knowing the others would be shocked and impressed by their youngest teammate. Robin climbed up to the top platform of the trapeze, waving at the onlookers before launching himself of the platform without a care. Wally laughed at the panicked look on his teammates face - there wasn't even a net below the trapeze (not that it mattered when they were literally all heroes - one who could run really fast and one that could fly). He proceeded to perform a whole act on the trapeze.

It was stunning. Robin flew gracefully, performing tricks left and right, seemingly flying through the air without any worries. He looked truly free in a way they rarely saw. After ten minutes of intricate tricks, Robin swung himself back onto the starting platform, took a deep breath and leapt off.

He did one flip.

Two flips.

Three flips.

Four flips.

...five flips.

Robin caught a lose rope, purposely hanging down the side of the trapeze, using it to control his fall. Landing on the floor with a forward roll, launching himself straight back to his feet and taking a bow. Grinning widely at his onlooking team mates. Their expressions ranged from smug (Wally) to bemused (Artemis) to amazed (M'gann) to mildly surprised (Conner) and oddly proud (Kaldur). They had gotten used to Robin using his acrobatics during fights but to see him perform like that on a trapeze was an entirely different matter.

"Was that a quintuple flip? No one's ever done that before! The best was the Flying Graysons who could perform a quadruple flip!" Artemis exclaimed, crossing her arms on her chest. Wally was the only one who noticed Robin's slight flinch at the Flying Graysons, though that was likely as he was the only one to actually know to look for it.

"Woah Arty calm down!" Wally tried to spare his friend. Calling her 'Arty' usually distracted her enough that she forgot her previous chain of thoughts.

"Answer the questions Boy Wonder!" Artemis continued ignoring Wally. She wasn't really expecting an answer, anytime they had asked before he had only offered a smug smirk. Which is why they were incredibly surprised when he did offer some answer.

"I did acrobatics a lot when I was a kid. I thought you guys deserved to know, plus there isn't much to do at the minute. Also, yes Artemis that was a quintuple flip, I've been practising it for a while." Robin replied calmly.

And that was clue number 1 for the team, he did acrobatics (at a very skilled level).

If only the team realized that Robin was giving them hints to his identity, they might have had a better chance to try and figure out his identity.