Kat Dennings thinks Kim Kardashian's butt is ''amazing.''

The '2 Broke Girls' actress was ''very nervous'' when the 'Keeping Up with the Kardashians' star filmed a cameo for the show's 80th episode and was too shy to tell the reality TV star, 34, how much she admires her famous curves.

The 28-year-old star told 'The Ellen Degeneres Show': ''I didn't know what to expect because she's so famous. I was very nervous because I've seen so many episodes [of 'Keeping Up with the Kardashians'], and she was very sweet. She was very nice. And her a** is amazing! I am feminism, girl power, but I was just so in love with her a**. I just spit talking about it - that's how passionate I feel!''

She added: ''She's gorgeous. It's just amazing. I've never seen an a** like that in my life. There's an episode of 'Keeping Up With the Kardashians' - an oldie, a vintage one, before she and [Kanye West] got married - and she was doing her music video and Kanye was there and he was like, 'I have never seen an a** like that.' And that's what I was thinking!''

Kat recently started dating Josh Groban after her co-star Beth Behrs introduced her to the singer, 33, and thinks he's a ''wonderful person.''

She said: ''He's very witty on the Twitter and I saw his little tweets...and sometimes we would [tweet back and forth]. But, yeah she's always talked about how great he is. They've been friends for years. And she thought we were both, you know, nerds. So there, she was right.''