Saved by the Bell - Season 1 Episode 4 -

Kelly has to choose between Zack and Slater to go to a big dance Bayside is having. Zack wants to make sure that he is Kelly's choice. In order to do that, he places a microphone in Jessie's room before her slumber party, which Kelly will be attending. Soon, Jessie discovers the microphone and Kelly comes up with a plan to play a trick on Zack, making him believe that she is a very dangerous soul.