Timothy "Tim" Drake replaced Dick Grayson as Robin.
Tim Drake was the son of criminal Steven "Shifty" Drake, a thug for the crime lord Two-Face. He had very little respect for his father, and often had to fend for himself. Around the age of 13, Drake began to idolize Gotham City hero Batman and placed newspaper clippings on his wall. After Batman left a batarang behind at a crime scene, Drake found it and began using it himself.
Adventures as Robin
When his father double crossed Two-Face, Drake was left a note and a key to a Gotham City airport locker. This key was discovered by Two-Face's henchmen when they briefly kidnapped the youth. Two-Face flipped his coin, and decided to execute Drake, but Batman had rescued the boy. Soon after, they discovered that Drake's father was killed outside of Gotham. With no place to go, Bruce Wayne adopted Drake and began to mentor him under his tutelage as the second Robin, the same time Dick Grayson rejoined the Bat-family as Nightwing.
Almost immediately, Drake began working in the field as Robin. One of his first acts was helping Batman thwart the Joker's attempt to kill Gothamites with a sonic bomb during a New Year's Eve celebration.
When Mr. Freeze began targeted assorted people in order to destroy people's hope, and went after Wayne's family, Mr. Freeze at first considered freezing Drake, the surrogate son, but ultimately decided to go after Alfred Pennyworth. Drake was left behind to watch over Alfred while Batman and Batgirl went after Mr. Freeze.
When the Scarecrow invented a gas that removed a person's fears, and Batman was turned into a man with a fearless attitude, Robin stopped Batman out of fear his mentor was no longer afraid to kill. As a result, Robin tied up Batman with his grappling hook. The Dark Knight pretended contrition and offered to let Robin lead if he let him go. Robin was nearly fooled, but saw through the façade just in time and left in the Batwing to find Scarecrow's hideout. When Batman nearly killed Scarecrow, Robin freed Batman with the antidote. With Batman back to normal, Robin was given Batman's praise for doing the right thing.
During one night of working solo, Robin came to the aid of a young girl with amnesia, developing a bit of a crush on the girl. She later proved to be a lost creation of Clayface in order to scout out Gotham for a return. Unfortunately, the girl had "forgotten" her purpose and continued to run. When Clayface reabsorbed the girl, Robin took her "murder" very hard and almost killed Clayface if it wasn't for Batman stepping in at the nick of time.
After fighting against pick-pockets and thieves, Robin asks why Nightwing left the Robin mantle. After hearing about his predecessor's last days as Robin, Robin and Nightwing learn about a night watchman at Wayne Enterprises. The two protégés of Batman leave when the Bat-signal comes on in the night sky to join Batman.
When Batman mysteriously went missing, Nightwing and Batgirl went to search for Wayne while Robin was left to defend Gotham by himself. When Superman arrived in Gotham, Robin teams up with the Man of Steel. With Robin as a guide, Superman was able to successfully masquerade as Batman for a time, and together, the duo discovered that Wayne was actually under Brainiac's mind-controlling nanites. They managed to save Wayne with Brainiac's destruction.
Later career as Robin
Sometime after Nightwing left to establish himself in another city, Robin was patrolling alone one night. Upon hearing a scream for help, Robin rushed to the aid of a lone woman being accosted by thugs when, in fact, he was falling into a trap set by the Joker and Harley Quinn. For the next three long weeks, in the ruins of the old abandoned Arkham Asylum, Drake was mercilessly tortured with electro-shock and chemical injections. During the course of these torture sessions, Joker extracted the precious secrets entrusted to Robin. Not content with just destroying Drake's mind, the Clown Prince of Crime sought to further humiliate Batman. To this end, Joker transformed Drake into a crude, childlike version of himself: Drake's skin was bleached white, his hair dyed green, and his mouth was twisted into a grotesque, Joker-like grin. Because of the torture, disfigurement and brainwashing he endured for three weeks, he was also rendered unable to communicate in any way except with demented laughter.
Renamed "Joker Junior", often shortened to "J.J.", Joker claimed the boy as his and Harley's 'new son', and planned on using Drake to destroy Batman. When Joker had managed to render Batman helpless, he gave Drake a gun to kill his adoptive father, although in a different version was the gun was fill with gas and to make him one of them. Drake began to laugh uncontrollably, and fought with the order to Batman. Eventually Drake ultimately refused the Joker's orders and killed him, although specific details vary: One version claimed he was able to overcome Joker’s brainwashing long enough to avert his aim from Batman to Joker, who he then shot, killing him on the spot. Another version had him throwing off Joker's control enough to toss the gun aside and then shove an irate Joker, resulting in the Clown Prince of Crime being doused with water tanks from his earlier torture of Drake and getting him tangled in the wires meant for the electrical generator. Joker then, consumed with fury, tried to attack Drake, but ended up slipping on a puddle and activating the electrodes, resulting in him being electrocuted to death with his agonized screams being loud enough to catch the attention of Barbara Gordon from outside the asylum. In either case, after Joker's death, Drake once again broke into hysterical laughter, which slowly turned into tears of despair, he completely broke down in Batgirl's arms. After these events, Batman and Batgirl buried the Joker deep beneath Arkham, and Commissioner Gordon quickly covered up the incident and none of the details were ever made public. After the trauma that he had suffered, Drake was broken both physically and psychologically, to which Dr. Leslie Thompkins spent a year treating him and a year later, Drake had finally recovered. After what had happened, Batman forbade him from donning the Robin costume ever again before Drake left, choosing to make the right decision for himself. Drake attempted several times to mend things with his former mentor only to fail. Despite his recovery, Drake would suffer horrible dreams of himself killing the Joker for years.
Over the next several decades, Drake had completely left the hero lifestyle behind him, becoming a top-level communications engineer, a husband, and father of two. He apparently ended up regretting ever being Robin and had even less love for the suit than the Joker did. Despite his apparent hatred for his secret life during his teenage years, he still had a relationship with Barbara Gordon. On the other hand, Drake's relationship with Bruce was rocky at best, as he felt nothing but bitterness and scorn for his former mentor. It was later revealed, however, that much of his hatred for Bruce and his time as Robin was caused by another source entirely.
During the time he was held prisoner by Joker, a DNA microchip with his tormentor's own memories and DNA was planted into Drake's spinal column. As the years passed, the microchip activated, allowing the Joker's personality to emerge and take control of Drake, explaining his increased hatred for the Robin identity and Batman. The chip would also physically transform Drake into an exact replica of the Clown Prince of Crime. Using the host's communication engineering skills to take control of a satellite with a powerful weaponized laser on board, Joker went on a crime spree. Ultimately, however, the new Batman (Terry McGinnis) was able to destroy the microchip, freeing Drake of the Joker forever.
Having had all along been unaware of what had been seeded inside him, Drake was taken to the hospital for his injuries, and was visited by McGinnis, Barbara, and even Bruce. Barbara had managed to cover up Drake's involvement in the incident, as he was technically innocent. As McGinnis took his leave to let Bruce and Drake catch up and both of them reconcile, Drake gave Terry the respect of being Batman, and he said that it meant a lot coming from him.
In the comics, Tim Drake was the third person to take the Robin identity while Jason Todd was the second holder of the title until he was killed by the Joker. Tim Drake's character in the animated series mixed certain elements of both comic-book characters together.
Like Jason, Tim was an orphan and a former thief living on the streets until he was taken in by Batman when his father disappeared after working for Two-Face. He also had a very rebellious streak that had a tendency to put him in trouble. Jason was also much more prone to be willing to endanger the lives of criminals if provoked and the animated Tim almost killed Clayface after his absorption of Annie. It is also worthy to note that, like Jason, the animated Tim's career as Robin was brought to a tragic and horrifying end by Joker, both involving torture (although Tim survived unlike Jason). Both also used at least one alias of Joker's as well: Jason used Joker's former Red Hood alias while Tim literally turned into Joker (although the reasons are different), and Jason willingly adopted his alias specifically to get revenge on Joker while Tim wasn't aware of Joker taking control of his body and mind. Parts of Animated Tim's tragedy were adapted in the Arkhamverse story of Jason, where instead of killing him, Joker tortures him in Arkham Asylum sending him insane, convincing him to become the Arkham Knight, though Jason was restored to sanity rather quickly and redeemed himself by rescuing Batman from Scarecrow. However, Tim did share a few qualities with his comic counterpart, in that he showed surprising knowledge and skill for detective work and was very adept at working with computers if need be. In the comics, Batman even admitted that Tim Drake was smarter than he was.