The world got to know Katharine McPhee in 2006 as a sweet-voiced breakout star on "American Idol" who ended up coming in second place. But as the now-26-year-old singer reveals on the upcoming episode of MTV's "When I Was 17," airing Saturday at 11 a.m. on MTV, she popped up on another reality-TV competition back in her teenage years.

"When I was 17, I went on this show called 'Ed McMahon's Next Big Star,' " she said. "It was this competition, and, oh gosh, it was awful. And I didn't even win! I never win those competitions. It sucks!"

It also seems like McPhee didn't always like competition with her friends either. As a high school senior, she was elected student body vice president, and ended up brawling with her best friend, who just so happened to be the school's prez. The dispute came about over a disagreement on the school's budget — specifically, whether their homecoming ceremony should be capped off by a massive fireworks display.

"She's like, 'I think we should skip the fireworks this year,' " McPhee said of her friend. "And I was like, 'Skip the fireworks? That's the best part of the entire homecoming. Everyone looks forward to it.' She's like, 'It's a waste of money. We're not doing it.' I'm like, 'Excuse me, this is a dictatorship? I see how this is.'

"We got into this really big fight and — I was so angry — I got up and she was standing by the door and I just rushed out the door and I brushed by her shoulder," McPhee continued. "She thought I intentionally rammed into her shoulder. We're in a catfight, and I was screaming hysterically, 'Stay away from me! Stay away from me!' because I was so angry, I was so upset."

Don't miss "When I Was 17" — this week featuring Kat McPhee, Bret Michaels and Kevin Jonas — Saturday at 11 a.m. on MTV.