@Woody1000: Exactly. It was in one of the Dilbert books (can't remember which one), and Scott wrote that Jim Davis asked him for the original, which he traded for an original Garfield. Scott said at the time it was his greatest financial return as a cartoonist.
@saywhatwhat: Agreed. I was only referring to the punchline. Both jokes are different and quite funny.
@ pbsalomone et al., I wouldn't call it a re-run. The line is the same but the joke is completely new, both times great. (It took a moment to get the old one, thinking back to kitty with suction cups on its feet.)