Dr. Foster, I Presume! The Worst Witch : Season 4 Episode 7

Dr. Starfinder is working on a machine to "get around" the Fosters effect; little does he know that Foster comes to him. The students are informed of the Fosters Effect. This rule, discovered by Doctor Foster, prevents magic being used for selfish or trivial reasons. Mayhem ensues as the 'missing' Doctor Foster contacts the college after having gotten caught in a spot of bother.