Chilli gets a prosthetic nose and a fat suit in an upcoming episode of "Celebrities Undercover." CREDIT: Oxygen

Credit: Rodney Ho

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Credit: Rodney Ho

The last person you'll ever see fat is Rozonda "Chilli" Thomas of TLC fame. At age 43, she's a serious fitness and nutrition buff with washboard abs.

"I don't think I could be a size 8 even if I tried," the singer said in a phone interview earlier this week.

So when Oxygen approached her to do "Celebrities Undercover," where famous folk disguise themselves to hear what regular folks think of them in their earshot, she was game for anything. (Her episode airs Tuesday, April 22, at 10:30 p.m..)

"If they wanted me to be a street walker, I would have been fine with it,' she said.

The decision: have Chilli wear a fat suit, a wacky wig and a prosthetic nose to play a casting agent for a fictional TLC music project.

"It turned out to be a blast," Chilli said. "It's the prankster in me. Everything about it was appealing to me."

She said she had a tough time looking the dancers in the eye, afraid they would figure her out. "I didn't want to get too close to the girls," she said.

CrazySexyCool Premiere Event on October 15, 2013 in New York City. Chilli of TLC will not look like Chilli on the April 22 episode of "Celebrities Undercover" on Oxygen. CREDIT: Getty Images

Credit: Rodney Ho

icon to expand image

Credit: Rodney Ho

Chilli is no stranger to reality TV. She and her TLC partner Tionne "T-Boz" Watkins did a show about finding a third singer (which was really only a temporary gig) on the UPN eight years ago. For two years, she tried to find a man on VH1's 'What Chilli Wants." (No luck there.) Last year, she competed in "Rachel vs. Guy: Celebrity Cook Off."

On that last show, she learned recipes from Guy Fieri she still cooks today, including a mango salsa she puts on fish tacos and an apricot sauce. She also finds herself obsessing over 'clean" plates, wiping stray sauce off her finished dishes before presenting them. (Not that her 16-year-old son Tron really cares.)

She is also beside herself with happiness that the VH1 biopic about TLC last year went over so well with the audience. "

"We have a whole new generation of kids who are TLC fans now as if we just came out," Chilli said.

After a show in Canada, she met a five-year-old girl who has seen the movie "a bajillion" times and wants to be Chilli. "She had a TLC-themed birthday party!" Chilli said. "She knows all our songs, even those that weren't singles!"

She and T-Boz are now doing spot tour dates but have yet to finalize a concert in Atlanta. She teased that the band might make its first concert appearance in Atlanta since the FanMail tour 15 years ago at Music Midtown. (She merely said they might come back in September and I noted that's when Music Midtown is happening. She didn't deny that might be the case .)

T-Boz suffers from sickle-cell anemia and has had bouts of illness over the years, limiting touring opportunities. Chilli said the good news is recently, T-Boz has been healthy and able to tour.

TV preview

"Celebrities Undercover," 10:30 p.m. Tuesday, April 22, Oxygen