(Strip Number 736, Original Publication Date, 29 October 1984)
Panel 1: We begin the trick-or-treat arc with Lawrence asking Michael where he got the Sherlock Holmes costume. A glum Michael whines that his mom made it.
Panel 2: As Elly listens in to their conversation, Darryl asks him why he didn't dress as a "rock star" to match the rest of them. (Given that Lawrence looks like Richard Simmons, Gordon looks like Shaggy Rogers and Darryl looks like one of Queen Beryl's generals, Lynn has a very strange idea of what a rock star should look like so it looks to me as if Mike fits in after all.)
Panel 3: He explains that his mom somehow or other thought that he'd get into trouble somehow or other were he to wear a costume that frightens her. This baffles the kids and they say so.
Panel 4: When one of the scruffy little fellows asks Mike if he's got any tobacco for his pipe, Elly's face freezes in the Bug-Eyed Glare of Existential Horror.
Summary: The reason for this is that Mike's Halloween experience has had a head-on collision with his mother's Boomer Truthiness. Since she feels in her gut that wearing the scary costume that scares her can only lead to disaster and (her) disgrace, any facts coming from her unfair brain about how she's only upset because Mike is thinking for himself and she's too vain and silly to deal with that have to be ignored. Otherwise, she'd look in the mirror and see the jerk mother the lady at the Easter parade saw and that would be just awful.