There was an animated segment which I first saw it on Noggin Unpaved probably from 1971 or 1972 about the letter M. Here's how it went:
A big gray man (which he's looking similar to the one in "Hey, Arnold!") is near the doorway and invites his friend for dinner. Then, the small-size capital "M" with eyes enters through the doorway. Now, we see a huge table that is filled with food and drink and the man lets him dig in. Then, the "M" began to eat the meats and the marshmallows, then he drinks the milk and wine and eats everything else that I could never understand the others. Afterwards, the man will never invite M to dinner again, because it was rude and makes the man not hungry. So the man plans to invite the "J" or a "Q" or any other letter but not other M's to dinner and the M began to eat the whole entire screen until it fades off by using his beak-like mouth like a bird.
A big gray man (which he's looking similar to the one in "Hey, Arnold!") is near the doorway and invites his friend for dinner. Then, the small-size capital "M" with eyes enters through the doorway. Now, we see a huge table that is filled with food and drink and the man lets him dig in. Then, the "M" began to eat the meats and the marshmallows, then he drinks the milk and wine and eats everything else that I could never understand the others. Afterwards, the man will never invite M to dinner again, because it was rude and makes the man not hungry. So the man plans to invite the "J" or a "Q" or any other letter but not other M's to dinner and the M began to eat the whole entire screen until it fades off by using his beak-like mouth like a bird.