This is not a bunch of jokes about Spears doing odd things over the weekend. Very powerful, very moving monologue from Ferguson on his own history of addiction, etc.
http://www.cbs.com/latenight/latelate/comedy/# (click on the Feb 19th monologue - if someone can figure out the direct link, more power to you)
I happen to think Craig is the best late night host on TV (with the exception of his scripted bits), and this is part of the reason.
EDIT: The audience clearly didn't know quite how to react at first. You can hear it in their chuckles at moments Craig didn't mean to be funny.