Sundance 2011: Paul Rudd laments fallen star of My Idiot Brother

What's likely to be the funniest film of the fest comes with a waggy tail tinged with pathos, Paul Rudd revealed in a Q&A after a rammed screening of My Idiot Brother .

The canine star of the movie, a mutt named Wille Nelson, popped his paws before production could complete, to be replaced in certain scenes by doggy relatives - his daughter and his father.

"It was a very sweet dog, an older dog" lamented Rudd to the packed out auditorium at the Eccles Theatre this morning.

Rudd plays dope smoking do-gooder Ned, with Elizabeth Banks, Zooey Deschanel and Emily Mortimer as his belieguered sisters.

Not such a far reach for notoriously laid back Rudd, mused one audience member; "Did you go method? Did you have to do much research?"

"I got the first part of that question but I was so high I was zoning out in the second..." joked Rudd.

But don't expect Dude, Where's My Car - the cast were keen to emphasise the good heart behind the comedy.

"It's hard to always try and see the good, to live your life according to that ethic. It's a difficult but gratifying way to live".

Bless! But don't worry - this is very funny stuff. The sold out theatre was booming with laughter throughout and as the credits roled the crowd went mental - take our word for it: My Idiot Brother is going to be a massive hit.

Rosie is the former editor of Total Film, before she moved to be the Special Edition Editor for the magazine group at Future. After that she became the Movies Editor at Digital Spy, and now she's the UK Editor of Den of Geek. She's an experienced movie and TV journalist, with a particular passion for horror.