Like Homer, the decades of repeated humiliation, embarrassment and dejection from the audience he entertained, jades Krusty's enthusiasm over his career until it turned him into a complete charlatan.Off-stage, Krusty has shown to be a manic-depressive, alcoholic, chain-smoking gambler which he states he became to deal with the stress of his job.Krusty is a hard-living entertainment veteran who has been down and out several times (always being rescued by the Simpson children) and remains addicted to cigarettes and alcohol (and, in two episodes, Percodan).
Krusty, throughout his career as a comedian, sold out and totally over-merchandised his name from his own fast food restaurant chain to toys, clocks, swabs, eye-dabbers, a clown school, Canyanero and Vodka rather than work on his own act.
Because of this he often steals from other comedians, a line from Pardon My Zinger being one he took credit for and saved Saddam Hussain from being assassinated because he was "half [of Krusty's] act" in his comedy bit.
Krusty is known to be best friends with Sideshow Mel, but Sideshow Mel is really just Krusty's sidekick. He also shares a relationship with Bart, who is Krusty's biggest fan and calls him his hero.
But while Krusty is fond of Bart and will often help Bart when he can, Krusty almost never remembers who Bart is and requires his memory to be coaxed and often just calls him "kid" rather than taking the time to use his real name, despite the fact that Bart saved his life on one or more occasions. He usually gets married to his sideshows, including Eartha Kitt.
This is the equivalent of providing the entire combined 2012 populations of Seattle and Washington, DC a nourishing meal.