(Strip Number 7228, Original Publication Date, 26 October 1986)
Panel 1: We start off watching Michael and Elizabeth as they plan to carve their pumpkins.
Panel 2: They set up the conflict by dumping the innards on a table because some idiot with poor planning skills forgot to give them a container where they can put the pumpkin goo so they don't slop it all over the table.
Panel 3: We set up the punchline when Mike reminds Lizzie that the key to a really good jack-o-lantern is putting the right expression on it.
Panel 4: Michael says you have to imagine a really weird, mean and scary face.
Panel 5: He then tells Lizzie that said hideous image of terror must be fixed in her mind before she starts.
Panel 6: When Idiot With No Planning Skills Elly finally overcomes her inertia and checks in on the children she gave sharp knives to, she sees the pumpkin pulp and startles the Hell out of the kids when she screams "Just look at this mess!!!!"
Panel 7: She then bitches about how she'd just cleaned the kitchen only to find pumpkin guts EVERYWHERE because she can't not turn into a ranting freaking maniac about piddly-crap.
Panel 8: Since spending five minutes cleaning up pumpkin guts is obviously part of a plot to oppress and destroy her, Humorless Git Elly glares at the kids.
Panel 9: As Elly stomps off to bitch to Annie or Carol about the evils of children making messes for her to clean up, Michael asks Elizabeth if she has the monstrous visage they've just seen locked in her memory.
Summary: The scary face I have in my mind is the one Lynn makes after losing her shit because snarkertrolls who want to take childhood away and enslave Elly would have her supervise her children lest they stab themselves. Only bad people who hate Lynn and have no faith in her (like us and Ursula) want Elly to supervise her children or be aware of what they're doing. Said cruel people also tell her the terrible thing "Jeez! LIGHTEN UP!!!!"