What what, in the butt?

While the lyrics to that Samwell song aren't exactly about cosmetic enhancement, those are the first words that came to mind when we saw singer Kesha's extra plump rear at LAX on Tuesday evening!

A source tells X17online the pop star had injections to enlarge her derriere, and very recently. Our insider tells us exclusively, “She wanted to follow the trend. She thinks a boost in her rump will give her career a boost as well.”

Kesha has been open about her body image issues, and after a stint in rehab for an eating disorder, she chatted with Vogue earlier this year. "There was a lot of not eating — and I started to think being hungry to the point of feeling almost faint was a positive thing," she says. "The worse it got, the more positive feedback I was getting. Inside I was really unhappy, but outside, people were like, 'Wow, you look great.' Every day I have to look in the mirror and make the choice to be kind to myself. This is who I am—I have to love that."

While we're glad that she's healthy and happy now, hopefully she doesn't go too crazy with the nip/tuck. Our source added, “Kesha wanted to feel better about herself. She had her boobs done years ago but this was the remaining thing that was bugging her — she thought her butt was too flat so she just had a little work done.”