Splinter?

Did he just steal the Teenage Mutant Ninja Turtles' origin story?

"Dude, if you want to stay all mysterious and shit, just say so. You don't have to lie about it."

Oh, it's not that Stiles doubt that he could run into people he thought were fictional. It's just that Raph is most definitely not a giant turtle.

Stiles catches the poncho Grace tosses to him, but doesn't put it on. It's like umbrellas, right? Don't open them inside.

He does grab some Twizzlers of his own, and a bag of Cheetos.