Knife Monopoly is invented by this person.

 

↓ Transcript
TODD: Thanks for dinner, guys.

MARI: Oh, you know it's our pleasure, dear.

MARI: Now, I want you to be sure to bring everone by this weekend for a game night while we have your sister in town.

TODD: Of course. Wouldn't miss it.

MARTA: KNIFE MONOPOLY!

STEVE: The deadliest game.

TODD: Don't pick fights you can't win, little sister.

MARTA: Oh, you'd better come ready to DANCE, boy!

AMANDA (dreamstruck): Knife Monopoly, you say...

TODD: Knife Monopoly isn't real.

SELKIE: But it coulds be...

Haggling in Knife Monopoly will cost you an arm and a leg.