Splash panel from "I Entered the Dimension of Doom!" in Tales of Suspense #23 (November 1961), plot by Stan Lee, script by Larry Lieber, pencils by Jack Kirby, inks by Dick Ayers, colors by Stan Goldberg, letters by Ray Holloway (?)
Puny li'l thing, ain't he?
He was given to me by these monsters from another dimension who were two-dimensional! I mean, man, they were flat out flat, baby! (Hey: where'd they keep that monster, then?)
Remember these simple tips for the caretaking of your new monster from the two-dimensional world: no bright lights, don't get him wet, and never feed him after midnight. And oh yeah: don't expose him to the super-growth vapor that makes him rampage and run amok throughout the civilized human world. That last one, mostly.
Luckily, the world was saved...by litigation!
So, this was a story about comic book characters who were two-dimensional. Well, as the man once said...aren't they all?