In the election of 2000 I was reading the paper one morning in early December and read something about how they hadn't counted all the ballots yet in Florida and I simply said out loud, "That is ridiculous. That is so ridiculous, it's ridonculous!" This, I believe, is the first time anyone ever used the word, to the best of my knowledge. It has spread like disease, though. I do think, however, we need to try and not overuse it. Some things are still simply ridiculous, not wholly ridonculous.
"You're an iron-clad beast-like machine with jaws of steel."
"I am not."
"Then you're Michael Jackson."
"OK, now that's just ridiculous."
"OK, then you're rhinocerous-like triceratops."
"THAT is riDONCulous!"