How to make other things depend on another

So I have been crating a pacman game and wanted to know how to make the ghosts turn into another ghost when pacman eats a power pellet.

You can make them play an animation

There’s a movie button in the Sprite editor

Using Message and Mailbox will get your job done. Action -> Message on your collision of pacman and the power pellet. Mailbox->Action on your ghost which triggers a switch for a different animation or whatever you want it to do.