Cheer Pressure : Season 7 Episode 12

The heroes encounter Thatcher, the boy they helped at the lighthouse, who joined a band of cheerleaders, named Pep Squad. Team Rocket decides to ally themselves with the Pep Squad's leader, Sheridan, who gives them an advantage during their battle with Ash and Brock. However, Max starts having suspicions and goes to check out what is coming from the drums the squad is playing.