Writer and producer Ken Levine posted a very interesting crossover in connection to the Super Bowl. It's a 'Cheers' scene that, like the 1984 MacIntosh blipvert, aired only once. Unlike that ad, it really hasn't been seen again. Levine is even afraid there's no longer a copy of it anywhere.
But he's posted the dialogue, which includes a serlinguist turn by the NBC "tout" Pete Axthelm.
You can read it here.
I consider it a true connection to 'Cheers', which means the crossover standings for all concerned have just been upped by one more link. That puts Norm and Cliff into the stratosphere with Munch in my book!