Chris O'Dowd has revealed Jon Hamm is not the sophisticated gentleman he would have everyone believe, but is in fact "a big goof".
The Irish actor and comedian has worked with the Mad Men star on Bridesmaids and new comedy Friends With Kids, and insisted he is nothing like the suave guy he plays on screen.
Chris said: "He's just a big idiot goof, who promotes himself as this brilliant dramatic actor but he's a bigger fan of poo joking than anyone I've ever met! That guy's the best, but he's so silly."
In Friends With Kids, written and directed by Jon's partner Jennifer Westfeldt and co-starring Kristen Wiig, Maya Rudolph and Megan Fox, Chris plays Alex, an exhausted father-of-two.
Chris, who is engaged to marry TV presenter Dawn Porter said he takes the character as a role model for when he becomes a dad.
Speaking at the Glamour Awards after party as he enjoyed smoking a cigar and sipping on Cointreau cocktails, he said: "I love the character even though he's a useless father. I hope that I have that exhaustive patience.
"I feel like I'm too uptight to be able to be good at that. I hope that I turn into the kind of father that Alex is."
The 32-year-old actor also revealed so far his wedding plans had got as far as tasting a lot of wine.
Other stars at the after party included The Voice contestant Bo Bruce, who stuck close to her coach Danny O'Donoghue all night as she enjoyed the party, along with Amanda Holden, Downton Abbey's Michelle Dockery and Myleene Klass.