I've been close friends with Katy since teenagers, before she was Katy Perry. She's always been a great resource for me to pull from and watch - from her choice of how public she wants to be about her personal life on down. I also watched her develop from the coffee-house singer-songwriter I knew to her be to playing arenas and killing it.

Cheating is bad. That's a big mistake I've made, and I've really hurt people. I've never lied about it, though. I've always been honest.

Sometimes I write a song and I'm down with it but I'm like yeah, whatever, and then everybody loves it and then it blows up. I'm like: "Okay! I didn't see that coming."

Obviously I love writing with Katy [Pery], I feel like we're the same person when we write together. Even though we fight a lot, we fight over every line and we pull each other's hair and we cat-fight all the time, it's always worth it in the end.

Ke$ha is super talented and super fun and always down to party - I love that girl.

When I go and write with other artists - a lot of the time it's with them - it's like a therapy session almost. I ask them what they're listening to and what they're going through and what their influences are and I try to get inside of their head and step into their shoes for a second.

I think one day I'd like to win an Oscar.