The 'My Life Would Suck Without You' hitmaker says she is always being mistaken for the country singer - but she doesn't mind as Carrie is ''100 pounds'' lighter than her.
Speaking on her own talk show, she said: ''That happens to me all the time! Seriously, I have been asked all the time or they'll be like, 'Oh my gosh, I love your song 'So Small'. And I'm like, 'I don't even know what that is.' And then, I'll find out it's Carrie Underwood! I'm like, 'Thank you!' Cause I'm, like, legit 100 pounds heavier than Carrie Underwood.''
Carrie and Kelly both won their series of 'American Idol' but the latter previously confessed she felt ''bitter'' for years after winning the talent show series.
The 37-year-old singer - who shot to fame when she took the crown on the first series of the talent show in 2002 - said: ''The first three years of my career was me just paying for winning a talent show. I got real bitter. I was just looking for anyone to talk to who knew what I was going through. And that's why I like to do that for artists on 'The Voice'. It's actually healed that bitterness I used to carry, being able to be that for somebody else.
''It's really funny, because I knew that the winner of Idol would have to do that movie and I didn't want to do that movie. And I think Justin [Guarini; who was runner up] did. So, we were totally cool with him winning and me not winning, so I didn't have to do [the movie]. But I won, and had to do it. Contractually obligated.''
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