Still, the funniest reference to this was in SUPERMAN/BATMAN: VENGEANCE when the Joker asks Mr. Mxyzptlik "Why don't they remember the time I had almost all your powers and tried to remake creation in my wacky image?" Mxy responds: "They don't remember because I don't want them to remember... also, it hasn't been collected in a trade paperback yet."
MOTTO.
And now that it HAS been collected, I'm waiting for an update.