Robin (aka Dick Grayson) is the leader of the Teen Titans. He is voiced by Scott Menville.
Robin is usually shown in just his costume that is consisted of green tights with black ankle-high steel-toed boots, green elbow-high gloves, a short-sleeve green t-shirt underneath a red armored vest with a yellow letter "R" inside a black circle over his left pectoral muscle, a yellow utility belt and a black cape that has a yellow interior. He always has on a black-and-white domino mask, has his black hair spiked backwards, light skin and an athletic-build. When he is briefly shown as Slade's apprentice, he wears a black bodysuit with armor plating on the legs, knees, forearms, shoulders, the top-half of his suit is split into black and orange sides and an ash-gray utility belt.
The most notable costume change he goes through is during the movie "Teen Titans: Trouble in Tokyo", he briefly changes into a costume with his hair down with black shades and a skinny black suit with a long jacket in order to hide from Tokyo Troopers when he was wanted for the "murder" of Saico-Tek. He took a man into an alley and switched clothes with him. He also wore a tux briefly in Date With Destiny. Robin might be short for his age. Out of his four companions, Beast Boy seems to be the only one shorter, and it should be noted that whilst Raven is usually depicted as the same height or a little shorter than Robin, there are occasions when she is taller. Also, in Calling All Titans, when he gave Bushido the communicator, Bushido seemed to be at least a couple inches taller than him.
In the Season 3 episode "Revolution", Mad Mod drains Robin's youth which makes Robin a frail old man and him young again. As an old man, Robin is so weak he can't even walk, he also seems to be very thin and his arms and legs are like bones. Robin is thin everywhere on his body except for his stomach where he seems to have grown a potbelly. While the young Robin wears his hair spiked backwards, the old and frail Robin has white hair which seems to be slicked back.
When Robin is Nightwing, he has long hair which almost touches his shoulders, he also doesn't spike his hair anymore. He also has a more muscular build and has grown much taller, his costume is a black jumpsuit with steel bracelets and a utility belt, he also still wears his steel toed boots. Nightwing's costume also has a symbol of a bird like a hawk, on his torso and it is a dark shade of blue. The bird on his costume also seems to be spreading its wings out as if it is flying.
It might also be true that he is around 4 ft. with reference to the episode Divide and Conquer when Cyborgs says " ....is 4 ft. tall and smells like cheap hair gel!" However this is unlikely as 4 ft is very, very short, and logic would suggest that Robin would be closer to 5 ft.
Robin is a natural-born leader. He is heroic, noble, kind, selfless, stubborn, brooding and usually serious in tone, but has had his number of funny moments. In DC Comics and other incarnations, Robin is even toned and playful despite some outbursts of rage; such as when he learns of his parents' killer and when he eventually stops working as Batman's sidekick (a situation that is mentioned in a roundabout way in the episode Go!). However, in this series, Robin is closer to Batman; serious, stern, strict and obsessed with hunting down criminals, which is most prominently displayed in the first season, where he goes so far as to masquerade as a villain to catch Slade. Despite this, Robin does maintain a more relaxed, at times even playful side, which he sometimes expresses when the team is not actively engaged in crime fighting.
Out of all the villains the team has faced, the one that is most hated is Slade. Robin will stop at nothing to defeat Slade. Robin insists that the two are nothing alike, despite Slade's claims to the contrary. Several encounters with him have lead dangerously close to causing rifts between Robin and his friends.
Another flaw Robin has is he is competitive and still a bit immature but, despite his struggles, Robin has time and again proven to be a great leader. He cares for all of his friends deeply, and will fight to the finish to defend them. Despite that Robin still remains as a calm, level-headed and intelligent leader who comes up with clever strategies, shows a lot of intellectual strength, and keeps a calm head most of the time.
Robin is a bit of a loner. Beast Boy and Cyborg hang around with each other more than him, Raven and Starfire are both independent but still interact with others, yet Robin often spends long days locked in his own room, planning. He insists on doing everything himself, such as being Slade's apprentice and battling Red X. In the episode Go! when the Titans first met, Beast Boy (who implied that he was a loner and hasn't had anybody to talk to since he left the Doom Patrol) wanted to befriend everybody, Robin made it clear that he doesn't want to be part of a team but eventually does form the Titans. Throughout the series, the team and everybody in it is very important to Robin.
He cares deeply about each of his friends, but for Starfire it is shown that Robin has romantic feelings for her. Everyone on the team can very well see their feelings for each other including the villains, but neither of them admitted their feelings until the movie Teen Titans: Trouble in Tokyo. During the film, Robin expresses horror when Starfire kisses a random Japanese boy to learn Japanese. Later, he and Starfire talk and nearly kiss twice, before they finally confess their true feelings for each other and actually kiss at the end of the film.