It seems like the cast of 'Friends' isn't as close as we thought they were.

David Schwimmer, also known as the nervous, wishy-washy Ross on 'Friends', is reportedly fuming with former co-star Jennifer Aniston after she insisted on 'The Late Show With David Letterman' that she doesn't know who his fiancee is.

Schwimmer, 43, announced his engagement to Zoe Buckman, 23, his girlfriend of two years, earlier this month.