One day you noticed your sister Mabel was behaving completely unlike her usual self, she's rude, mean, harsh, all those other words, you think it's either a clone, a shapeshifter, or someone just did something to her, but regardless, you're gonna find out what happened to her, with your brother Dipper's help

You and Dipper are questioning Mabel right now

Dipper: He's holding a notebook and a pen

Mabel: This is stupid