Despite joining in with the rest of the family to laugh at Kevin for being an incompetent squirt who can't pack his own suitcase, Megan expresses some sympathy for him. This isn't true at the beginning. When Kevin complains about packing his suitcase, Megan says:
MEGAN: The dope was whining about a suitcase. What was I supposed to say? "Congratulations, you're an idiot?"
But while they're at their uncle's apartment in Paris and feeling bored while watching a French version of It's a Wonderful Life, she tells Buzz that she's worried about Kevin:
MEGAN: He's so little and helpless. Don't you think he's flipped out?
This provokes Buzz's dumb speech about all the reasons she shouldn't be worried. Yet, when Buzz says "The little trout can use a couple of days in the real world," he speaks truer words than he and Megan realize. Kevin's becoming a booby-trap expert, capable of wrecking either of them if they ever cross him again.