Ribwich

The Ribwich was an item on the menu at the Springfield fast food chain Krusty Burger.

The Ribwich consisted of only the meat, the bun, and barbecue sauce. It was specifically not marketed as being nutritious or healthy. In the TV commercial for the Ribwich, the voice-over said, "We start with authentic, letter-graded meat, and process the hell out of it." The box the Ribwich was served in advertised it as "Now without lettuce!"

Homer tried a Ribwich and quickly developed a voracious appetite for them, eating so many that he became delirious and slobbered all over the place, prompting the Squeaky-Voiced Teen at the counter to call for a "Drool clean-up at Register 4!" Homer became hooked on Ribwiches, making frequent return trips to Krusty Burger to eat more of them.

Much to Homer's dismay, the Ribwich was a limited-time-only offer at the Springfield Krusty Burger. However, because the Ribwich was being test-marketed nationwide, it was essentially on tour and would soon be served at another Krusty Burger. Homer got a copy of the schedule and joined up with a large throng of "Ribheads" who

were following the Ribwich from place to place as it was released.

The last stop of the Ribwich's tour was in San Francisco, where Krusty the Clown appeared in person and announced that the Ribwich would not be made anymore, as the unnamed animal whose meat was used for the burger had become extinct. Krusty held up the very last Ribwich and threw it to the crowd.

Homer caught the last Ribwich, but he gave it to another person in exchange for his car, because he needed the car to get to the Spell-Lympics.

References / Trivia

The Ribwich is an obvious parody of the McDonald's McRib sandwich, which is also noted for its intermittent availability and the less than obvious origin of its meat.
The "Ribheads" following the Ribwich are a reference to Deadheads, fans of the Grateful Dead who followed the band as it toured.
When Krusty finishes talking to the crowd, he says, "What a long strange product rollout it's been," which is another Grateful Dead reference.
The animal from which the Ribwich is made is never specified, but when someone mentions a pig as a possibility, Krusty replies, "Think smaller, and more legs." It could possibly be an insect or an arachnid.