Kat to the Future: Parts 1 & 2

Kat to the Future Part 1: Coop uses Kat's time machine to go back to the past and stop Millie from bringing Kat home, but ends up altering the future for the worse. Kat to the Future Part 2: Coop tries to undo the Kat invasion, which he brought about by fooling with Kat's time machine. How will Coop undo the Kat invasion, and get back to the present before it's too late?