Chelsea Handler Threatened to "Tape Record" Reese Witherspoon on the Toilet

Chelsea Handler has taken potty humor to a brand new level.

The 36-year-old TV host became fast friends with Reese Witherspoon while shooting This Means War in 2011 -- so much so that she tried to pull a few pranks on the Oscar winner.

PHOTOS: Reese Witherspoon's best hairstyles ever

"She is just so ridiculous," Witherspoon, 35, tells iVillage. "She always threatens to tape record me when I go to the bathroom because I have a microphone on. I purposely take off my mic and put it somewhere else when I have to go somewhere. But she caught me singing a Rihanna song backstage."

VIDEO: Chelsea Handler complains that Reese Witherspoon is making her "crazy"

Despite Handler's antics, Witherspoon says the comedienne -- who also counts Jennifer Aniston and Charlize Theron as BFFs -- is "very sweet."

"She's a really great friend. She's the kind of person who will cancel all her plans if you're in a bad mood and you just want to sit on the couch and watch a movie," Witherspoon says. "She's really generous. She likes to give a lot of good gifts!"

PHOTOS: Reese Witherspoon's red carpet evolution

Handle r isn't the only celeb Witherspoon admires. "I love Gloria Steinem. I think she's incredible," says the actress, who lists Holly Hunter, Frances McDormand and Diane Keaton among her faves. "[I respect] women who've really had long and wonderful careers where they create great characters and just seem to be endlessly interesting and fascinating to watch."

Get more Us! Follow us on Twitter, Friend us on Facebook, Subscribe to Us Weekly