The first alcoholic beverage?
I was watching that clip on YouTube in which a man invites an "M" to dinner, and the letter wolfs down everything rather quickly and enthusiastically.
Look carefully as he commences eating. First he eats a steak in one gulp. ("Mmm....meat!") Then he eats something that's hard to identify, possibly prime ribs; all the M identifies it as is "Mmm...munch!" In between those two items, notice that the M takes a sip of (gasp!) wine! Could this be the first instance of someone drinking alcohol on Sesame Street? Yeah, I know it's really no big deal, and it's been proven that a glass of wine with dinner is actually beneficial healthwise, but there are still some soreheads out there -- the ones who wanted to ban "Little Red Riding Hood" because in some versions of the story she includes a bottle of wine among the goodies in the basket for grandma.
Also, note the M doesn't "credit" the wine, since that doesn't begin with the letter M. Could he have said "Mmm...Manischewitz, Merlot, Mogen David" and gotten some product placement in while he was at it?
Where have I seen this artist before? Is this the same guy who did The Adventures of Letterman on The Electric Company?