Recently it was announced that David Dastmalchian had been cast to play Abra Kadabra on an upcoming episode of The Flash. Now Kadabra has been part of some interesting Savitar speculation lately and seeing him announced gives some extra credence to the idea. But let's put that aside for now and focus on the comic book history of Abra Kadabra.
Abra Kadabra first appeared in The Flash #128 in 1962, created by John Broome and Carmine Infantino.
In the 64th century, science has made stage magic obsolete. But one Citizen Abra wants to be a magician so bad that he is willing to steal a time machine and travel back in history to find an audience. That is some serious dedication to a craft. Mind you none of his tricks are magic, or even slight of hand, but rather future technology. He even has a hypnotic device that makes people clap whether they want to or not. But he didn't get the desired fame once in our modern time, so he decided to interject himself into bigger events and steal things… which put him in conflict with the Flash.
The two would face off against each other multiple times, Kadabra using his future technology and hypnosis to get away or escape from prison, but overall Flash thwarted his plans on a regular basis. Once Kadabra went back to the 64th century where authorities made a device causing anyone around Kadabra to clap, quelling his desires to go back and mess with the Flash. Instead he brought the Flash to the 64th century and framed him for Kadabra's murder. But the tech-magician wasn't dead, he went back in time to commit crimes while the Flash was incarcerated in the future… but Jay Garrick stepped up and helped free Barry Allen and stop Kadabra.
Kadabra played a big role in one of the biggest Flash stories, the Trial of the Flash. Kadabra made a bet with the High Commissioner of the 64th century that he could change how the Flash dies. Since Professor Zoom had died in the 20th century, time had become malleable and Kadabra planned to pull Flash to his future to change time before it became solid again. If it works, the High Commissioner must declare magic a noble art again. Kadabra went back and posed as Zoom. He destroyed the police records on the Rogues, stopped Pied Piper from escaping prison and trapped Mirror Master, Weather Wizard, Trickster, Captain Cold, Captain Boomerang and Rainbow Raider in a rock formation outside of Central City. Kadabra then posed as a juror on the Flash's trail for killing Zoom, making sure the verdict was guilty. His final act was to destroy city hall with Flash and the juror inside. Flash survives and chase after who he thinks is Zoom to the 25th century where they discover evidence that it was Kadabra. They would go on to confront Kadabra but get captured, only to have the trapped Rogues show up after breaking free and using the cosmic treadmill to follow. The Rogues and the Flash work together to stop Kadabra and sending him to prison. But the magician got what he wanted, as the Flash's time was change, leading him to die in Crisis on Infinite Earths a few months later.
Kadabra would confront Wally West a few times when he was the Flash, Abra Kadabra makes a bargain with Neron: giving him magical powers in exchange for luring several members of the Rogues to their deaths. This gets him a seat in Neron's inner council, but when they broke the seal on Neron's soul jar, they were teleported away, only to return after Neron's defeat.
Kadabra would next try to destroy the Flash (Wally) on his and Linda Park's wedding day, taking her, wiping her memory and putting her on an alternate Earth. Wally teams with his alternate Earth twin Walter and to battle Kadabra. It appears that Kadabra kills Wally and Linda, then he teams with Replicant and Professor Zoom to take on Walter. But Walter tricks Kadabra into restoring Linda's memory and accidentally wipes his own.
Kadabra is recruited by Inertia to help, along with the Rogues, in a plan to create a device to freeze time. But Kadabra's advanced knowledge of time technology makes him aware that the device is not what Inertia claims. He is there when several other Rogues accidentally kill Bart Allen after the machine steals his speed.
And then Kadabra, along with other Rogues, are transported to the planet Salvation. He figures out that there are safe zones and works with a team to find them, eventually joining up with Lex Luthor and leaves the planet through Lex's teleporter.
In DC: Rebirth, he first appeared as an inept party magician named Mr. Hocus Pocus, but when Lilith tries to use her psionic powers to uncover Wally's 10 missing years, she awakens Kadabra. He tries to force Wally to run into the Speed Force, but Wally has yet to meet Linda at this point, so the anchor that always leads him back out of the Speed Force isn't there. But Wally uses the Teen Titans as his anchor to return.
Most of his appearances are basic bad guy and minor to the characters development. The key thing, in connection to the one fan theory, is that Kadabra was able to simulate super speed enough to pose as Zoom. Which means the theory that Kadabra is Savitar is at least plausible. There are other, equally compelling theories, but this one was one of the most unique and ties into deep Flash history.