His first chronological appearance was in Batgirl: Year One battling Batgirl ( Barbara Gordon) and Robin (Dick Grayson) and lost. Years later he was jokerized during the time Joker thought he was dying (Joker's Last Laugh). He was confronted in a mall by Ted Kord, Black Canary and Tim Drake who all vastly underestimated him, believing him to be a loser. However he revealed that during his stay in Arkham, Poison Ivy taught him more about spices which he put to use in his newest "recipes." He used his condiments on the three heroes sending them into anaphylactic shock, until Beetle used the milk to stop the burning, and remove the bomb from the mall as Condiment King is recaptured.
Recently he was easily defeated by Tim and Batman. He has joined forces with General Immortus and other new second-rate villains. Condiment King was responsible for the Human Flame's introduction to General Immortus and Professor Milo. His head was squashed by an outraged Human Flame.
After DC Comic big Rebirth, Mayo is seen alive and in Arkham Asylum.
Condiment King has weapons that shoot out various condiments, he's been known to use his knowledge to cause anaphylactic shock. It was stated the villains Immortus works with have received upgrades. Whether Condiment King received upgrades or not has yet to be seen.
Condiment King appeared in the Batman: The Animated Series episode entitled "Make 'Em Laugh"
Condiment King appeared in the Harley Quinn episode "Thawing Hearts", where he is seen to be the nemesis of Kite Man.