Sixth grade is just out of this world... Susan Simmons can tell that her new substitute teacher is really weird. But she doesn't know how weird until she catches him peeling off his face -- and she realizes that "Mr. Smith" is really an alien! At first no one will believe her -- except Peter Thompson, the class brain. When Peter and Susan discover Mr. Smith's horrible plans for their classmates, they know they have to act fast. Only they can...

It's Christmastime and Jack's new substitute teacher, Mr. Clausen, teaches the class how to make paper snowflake wishes, all the while reminding the class of another gentleman with a long white beard who enjoys a snack of milk and cookies.

Sam, Lucy, and Antonio have a new substitute teacher, who happens to be the great-great-grandson of Orson Eerie, the evil scientist whose spirit possesses and infects their elementary school--and the friends are afraid he may be trying to bring Orson back to life.

When a sinister substitute teacher takes over their class, it is up to Eugene and the rest of the Sunnyview Superhero Squad to find Ms. Beasley and foil the sub's plot.