i.e. can you stop someone playing a “Memo to Your Future Self” by playing a Memo or using the Cake card’s Memo ability?

A: Yes, a Memo can indeed be used to stop another Memo. And it’s mighty satisfying when you do! This also applies to the similar cards found in the Back To The Future card game.

“Looks like I Got There First to your dinosaur trap, and captured that Stegosaurus you thought you had.”

“Oh no you didn’t, because I sent a Memo to myself, telling me that you’d get there before me, so I got there 15 minutes before you, so actually, I still have Steggy.”

“Oh yeah? Well I sent myself a Memo telling me that you were going to get there 15 minutes before I got there before you, so I got there 15 minutes before you got there 15 minutes before me getting there before you, so actually, the dino is mine…”