A brain tumor allows a person to change the past by reflecting at relevant pictures.

Dave Bristol: [to Nick] You keep your shit together. Okay? I can't have you pop another brain fart and fuck this thing up.
[making out with Grace in the men's bathroom]
Nick: Hold up. Your dad's right outside.
Grace: I don't care about that, and neither does he. Besides, I'll just tell him to give you another raise.
Trevor Eastman: I've brought my own special birthday candle...
[shows joint]
Trevor Eastman: ... It's drugs!
Julie Miller: Oh! My favorite.
Amanda: ...Light it up!