Ambush Bug's true name was supposedly Irwin Schwab, but it must be noted that he suffered from mental problems that prevented him from truly understanding reality around him, so even his true identity might be no more than a delusion on his part. His origin is disputed, although the most commonly accepted origin is that Brum-El of the planet Schwab sent his clothes from his supposedly doomed planet, hoping that his wardrobe would survive, only to have it intercepted by a giant radioactive space spider. In the resulting crash, only two articles of clothing survived: the Ambush Bug suit, which was subsequently found by Irwin Schwab, and Argh!Yle!, an argyle sock with a metal mask.
At first, Ambush Bug was a villain, named after a type of insect, and dressed in a green, skintight suit (with two orange antennae) that covered his whole body. Inside his hollow antennae, he carried miniature robot bugs that possessed the ability to teleport him around. After attacking Superman and other heroes (and being little more than an annoyance to them), Ambush Bug decided instead to be a superhero as well. He also fancied himself Superman's friend, which only annoyed the hero even more. The costume apparently then became permanently affixed to his body, and he gained the power to teleport by himself. (Again, it's unknown if this was true or just another delusion of his, as he was later seen removing the costume.)
At one point, he picked up a doll, and, thinking it was alive, 'adopted' it as his partner, calling it Cheeks, The Toy Wonder, complete with its own costume.
He became something of a joke to other heroes.
In the limited series Son of Ambush Bug, he was an out-of-favor with the editors. Schwab was forced to make due with no funding. In a long, convoluted chain of events involving Argh!Yle!, repeatedly dying, and avoiding being retconned by a cosmic interloper, he left the DC Universe "forever", leaving behind his suit. For the first time, Ambush Bug's face was seen, an unfinished outline, with two lines across eye level. Given the Bug's return to the DCU recently, it is likely that either he made up with the editorial staff, or that the entire series is non-canon.
Ambush Bug joined the short-lived Justice League of America, organized by Firestorm several months after the Infinite Crisis.