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.