Olympian and "Dancing with the Stars" contestant Ellen DeGeneres's sneaky pranks.

The gymnast got quite the scare while sitting down for a recent interview on "The Ellen DeGeneres Show." Although the talk show host warned Biles that her "DWTS" partner, Sasha Farber, is a "prankster," the gold medalist was completely caught unawares. This worked out well for viewers, because it made for a priceless reaction when Farber did finally pull a prank on his co-star.

The professional dancer and DeGeneres get a 10 for their work. As simple as their prank was, they executed it executed perfectly and were rewarded with a terrified shriek any practical joker would hope for.

Watch Biles's appearance on "Ellen" below, and keep an eye out for the flawless prank around 3:50.

If you want more of Biles and Farber, you can catch them on "Dancing With the Stars" on Mondays at 8 p.m. ET/PT on ABC.