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I seem to have a vague memory of an alien wearing a helicopter beanie in a book published by MAD Magazine. This would have been quite far back (60's, 70's or early 80's), and had a format like a comic book or graphic novel, i.e. panels and word balloons. If you think I'm going in the right direction, I will keep looking.
KEVP
It wasn't a comic. In fact, I don't remember it having any interior illustrations at all. However, the cover did have an illustration of the beanie-wearing alien, and I remember he kind of looked like a turnip with spindly limbs and a face. There were also two human kids on the cover, and I think they had shocked/scared expressions, but I'm not sure on the last part.

Ugh, this is a book I read 4-5 years ago, but I think it was old back then already. I don't remember the specifics, but it involves an alien invasion, and at one point an alien disguises himself by putting on a helicopter beanie with the rationale that kids on TV wear those kind of hats and never get in trouble. And it actually works, because the hat is so ugly everyone pays attention to it instead of who's wearing it. The rest of the book is similarly hilarious, but I can't remember any more details.