DBZ Episode 203
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Rescue Videl is the ninth episode of the Great Saiyaman Saga and the two hundred third overall episode of Dragon Ball Z. The original Japanese title is "Gohan, Kinkyu Shutsudo! Biideru o Sukue!" (悟飯、緊急出動!ビーデルを救え!!).The episode first aired on October 20, 1993. It's original American air date was September 19, 2001.
It starts out with Gohan flying to school as the Great Saiyaman and runs into Videl on the way. She starts to chase him in her helicopter determined to find out who he really is, while destroying the city. They chase for a while and then stop when on ground, she asks the Great Saiyaman who he really is and gets another "I am the Great Saiyaman" declarations. By relocating Videl's helicopter to a roof Gohan escapes her, leaving Videl grounded while he takes off.
When she arrives to school she is pardoned for being a crime-fighter when arriving late. School is normal until the Red Shark Gang arrives. They kidnapped the Mayor and want Hercule to come fight them knowing he's a phony. While this is happening he is hiding like the coward he is, refusing to fight. So while Videl is excused from school to fight the Red Shark gang, Gohan has to wait until an earthquake hits (by tapping his foot on the floor) to sneak out and fight. He transforms into the Great Saiyaman and takes out the Red Shark gang, while Videl takes care of their leader. The day is saved and Videl thanks Saiyaman for his help, though she vows to unmask him someday.