From the Super Mario Wiki, the Mario encyclopedia
Crimewave Clyde is a large, muscular, and aggressive prisoner from the Real World who had been sentenced to jail for 12,423 years with no parole due to his extensive criminal record.
In The Adventures of Super Mario Bros. 3 episode "Crimes R Us", Bowser and his Koopalings travel to Clyde's prison on the Doomship, where Bully Koopa abducts him. Under the request of Bowser, Clyde agrees to teach the Koopalings everything that he knows about crime, so that they can grow up to be hardcore criminals. Bowser also tells Clyde that he can keep half of whatever is stolen in exchange, but he crosses his fingers behind his back when he says so.
Clyde's first lesson to the Koopalings is bank robbery. After they receive a crash course from Clyde, the Koopalings raid the First Mushroom Bank, but are foiled by Mario and Luigi in the process, although they do manage to escape.
Realizing that the Koopalings failed lesson one, Clyde makes some adjustments to his lesson plan, making sure that getting rid of the Mario Bros. is lesson two. The first step in this lesson is to have Cheatsy steal the lunch money from a Mushroom boy in Desert Land, whose cry for help travels through a Warp Pipe and alerts the Mario Bros. The boy directs Mario and Luigi to a pipe, which traps them in an underground maze where Clyde and Big Mouth lock them in with a Boom Boom.
Afterwards, claiming that he has taught the Koopalings everything he knows about crime, Clyde lets them run amuck in the Mushroom Kingdom, where they steal whatever they choose to steal. However, Clyde is pushed too far when the Koopalings not only start stealing from each other, but his own pockets as well.
When Bowser proposes to have his Koopalings steal one billion Gold Coins from the Mushroom Kingdom Treasury, Clyde only agrees to help, just because half of the loot is enough to relieve him from all the stress the Koopas cause him. To Clyde's surprise, the Koopalings double-cross him, and handcuff a Bob-omb to his ankle, although he manages to extinguish the fuse before it blows up.
Angry that he was double-crossed, Clyde breaks into the maze that Mario and Luigi are trapped in, and begs them to get him back to the Real World. After offering to help them stop the Koopalings from robbing the Mushroom Kingdom Treasury, the Mario Bros. reluctantly agree.
After the Koopalings invade the Mushroom Kingdom Treasury and begin packing up the loot, they are surprised to see Clyde with Mario and Luigi waiting for them behind a vaulted door. Before the Koopalings can react, Clyde and the Marios tie them up, and send them up into the Doomship, along with a Bob-omb. When the Doomship is partially blown away, fireworks are formed, while Clyde feels proud of the fireworks.
However, the Mushroom Kingdom is not recognized by the United States government, which means that Clyde's heroism there is not considered a case for clemency. As Clyde is still a prisoner in the Real World, Mario and Luigi are obliged to return him to his jail cell, which Clyde agrees to. Following his return to prison, he then befriends Mario and Luigi, who pay him visits at the prison's visitor center. While the Mario Brothers consider Clyde's sentence onerous especially since he has reformed, Clyde notes that he will gladly serve his 12,423-year prison sentence with no parole compared to spending one more day with the Koopas.
Crimewave Clyde's name could be a reference to Clyde Barrow of the notorious outlaw duo Bonnie and Clyde.