Carrie Coon, Finn Wolfhard, and Mckenna Grace star in the film as the aforementioned family of three. Paul Rudd also stars as a Summer school teacher named Mr. Grooberson who just so happens to be a Ghostbusters fanatic. A handful of actors from the original franchise are also reprising their fan-favourite characters, including Bill Murray, Dan Aykroyd, Ernie Hudson, Sigourney Weaver and Annie Potts.