In "High School Mystery," Holly's high-school principal Mr. Frost (Joe E. Tata) hires the Mystery Girls to make sure he does not become the target of the senior prank before he retires. When the detectives go undercover at West Beverly in order to stop the culprit, Holly realizes this job is her chance to have the normal high school experience she never had but always wanted. Desperate to fit in, Holly becomes obsessed with being popular and momentarily forgets about their case while Charlie takes her role as a gym teacher a little too seriously. Once the mystery is solved, Holly asks Mr. Frost for her long-awaited diploma, prompting the student body to start chanting "Holly Hamilton Graduates."