Burp the Twerp was originally created for Police Comics and publisher Quality Comics, in 1941. When Quality Comics went bankrupt in 1957, the rights to Burp the Twerp were bought by DC Comics along with many other Quality characters.
Though Burp is often thought to be a friend of Plastic Man, in actuality they have only met twice. The first meeting was in Police Comics #23, where Burp bragged to a reporter about how much tougher he was than Plastic Man then fainted when the hero himself showed up. The second meeting was also Burp's first and last appearance in a comic published by DC. Secret Origins #30 had Burp as a running gag, though Plastic Man did express some nervousness about offending Burp.
Burp, like many Quality Comics characters, has not appeared since.