When Dipper wishes he could go back in time and undo a mistake he made, he discovers there is a time machine that can help him do just that. Meanwhile, it's love at first sight for Mabel when she wins a pet pig at the fair.

Dipper feels self-conscious that Mabel is taller than him and is becoming the alpha twin, so he seeks out a magic way to grow himself the same height. Meanwhile, Lil' Gideon takes advantage of Dipper's and Mabel's height discrepancies.