Now we know: If we get stuck in a pile of muck, we're not calling Julianne Hough. If she won't jump in to help her own brother, she's not gonna help us. Thankfully, three-time Dancing With the Stars champion Derek Hough wasn't actually trapped, he was just helping his two-time champ sister get "Punk'd" on MTV.

Twilight star Kellan Lutz was in charge on Punk’d this week and he tagged in Derek to pretend to drive Julianne to a meeting, until they were stopped by a "roadblock." Derek tried to move it and fell into the muck, getting completely covered. Julianne didn’t try to save him and she also had no sympathy for an actor having a "panic attack" as he tried to save Derek. (Would she have helped Ryan Seacrest?)

Watch the video clip. It's pretty classic. Props to Derek for getting so gross in the name of comedy.

Source: Huffington Post

Gina Carbone is a contributing writer at Wetpaint Entertainment. Follow her on Twitter @ginacarbone.

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Credit: 5Min Photo: Derek Hough Pranks Sister Julianne Hough on MTV's Punk'd (VIDEO)