Don’t terminate this video of Arnold Schwarzenegger pranking gymgoers until you’ve watched the whole way through. The bodybuilding legend takes on the role of moustachioed personal trainer “Howard Kleiner,” who dispenses questionable (and hilarious) fitness advice to the real-life patrons at the Governator’s old training ground, Gold’s Gym. Their reactions are priceless.

The video (in which Arnold looks like he’s having a blast) is part of a campaign to raise money and awareness for the After School All-Stars, a nationwide charity that provides tutoring, physical education, and exciting activities to children of low-income families. It’s a great cause; we hope he’ll be back.