Barney, played by Giamatti, is in love for the first time in his life. Problem is it's not with the woman he just married, wife number two, but a guest at the wedding. And down the line, she becomes wife number three.
"It's comic and you start, hopefully you start, laughing from early on," said Rosamund Pike, who plays Barney's third wife. "Then it twists your gut and surprises you, and those are the stories I like to read."
"You're meant to feel like you lived through 30 years of somebody's life so hopefully it feels like that," said Giamatti.
"With all the mess and chaos and humor and romance and pain that goes with it," said Pike.
The roles required both stars to age gracefully.
"We had a face full of prosthetics but they were delicate," said Pike.
"They were great," said Giamatti. "The guy was amazing. He's the best special effects make-up guy I've ever worked with. He was great."
Dustin Hoffman plays Giamatti's unconventional father. Giamatti found him fascinating.
"I could never tell how much he really was like this guy or not," said Giamatti. "Whether he was doing some old school method thing, because he kind of seems like this guy off camera."