As I've mentioned before, a lot of these comics were themed according to the book that they were appearing in - Aquaman comics, for instance, were well-stocked with one-pagers about skin-divers. Batman comics took things a bit further by featuring a whole family of comics themed around crime and punishment: "Casey the Cop" chased "Lefty Looie" the thief and threw him into a prison (setting of "Jail Jests") administered by "Warden Willis". And they all crossed over: Casey sometimes worked at the jail; Warden Willis and Lefty Looie showed up in "Jail Jests", etc. For throwaway gag comics, there was a surprising amount of backstory.
Here's Lefty Looie:
Yup, that's a painted-on outfit, years ahead of its time. Might need a bit more thought, though.
Mostly, though, I keep on thinking about how sad Looie must have been once he realized just how hot a layer of paint can get. Poor doofus.
- from Batman no. 137