Paul Rudd, Jason Segel Embrace Guy Love

What's a man to do when he discovers, after getting engaged to the woman of his dreams, that he has no male friends close enough to be his best man?

Like a single searching for a soul mate, he enters the dating scene all over again to search for the one, but this is the one with whom he wants to drink beer and watch football, not walk down the aisle.

In "I Love You, Man," Peter Klaven (played by Paul Rudd, of "Knocked Up" and "The 40-Year-Old Virgin") proposes to Zooey (Rashida Jones, of "The Office") who excitedly calls her girlfriends with the good news and asks him if he wants to call his. Klaven suddenly realizes to his dismay that he's a "lonely man" who doesn't have any good male friends. To rectify this, he goes on a series of bizarre, awkward man-dates until he meets Sydney Fife (Jason Segel, of "Forgetting Sarah Marshall").

VIDEO: Paul Rudd and Jason Segel singPlay

Both actors recently sat down with ABC News Now's "Popcorn With Peter Travers" to talk about their romantic comedy, in theaters March 20.

"The movie really picks up when I arrive," joked Segel; "Yeah, that's when it really kicks in," grinned Rudd.

Written and directed by John Hamburg, who previously wrote and directed "Along Came Polly," "I Love You, Man" is a story about platonic love between two grown men. It's convenient that the actors' friendship is palpable -- the two became fast friends on the set of "Knocked Up." As Rudd put it, "I like to say we're on the same sunbeam."

Segel offered an anecdote about his own guy love: He and his childhood best friend lived together until a year ago, when his friend left for medical school. For Segel, the feeling of loss was unexpected.

"I had a dream. We were just hanging out not doing anything special, but when I woke up I had tears streaming down my face, so I called him and told him I missed him," said Segel in a rare serious moment.

"That's weird," joked Rudd. "I live with my wife, which is weird. We even have the same bedroom. That's the problem with New York apartments and the bad economy."

Asked whether they watched any "buddy movies" or romantic comedies for inspiration, Segel said "Fried Green Tomatoes" only to be one-upped by Rudd's answer: "Sophie's Choice" -- "a great comedy," he sagely noted, with Segel nodding in agreement.

Explaining their clear lack of research, Segel declared they wanted to reinvent a whole new genre. Their "comedic gold," as Rudd described it, wasn't lost on Hamburg, who allowed them to improv as much as they wanted. To keep them in line, Rudd recalled Hamburg saying, "there is a crew of 50 people who want to go to lunch now."

The two even offered an impromptu rendition of "Confrontation (Javert & Valjean)" from the Broadway musical "Les Misérables," before mixing up their parts half-way through the song, prompting Travers to put an end to the performance.

Rudd and Segel said they're fans of each other, and Segel praised Rudd, saying, "Paul plays a character who always gets things a bit wrong. He tries to give me a nickname 'Jobin,' which makes no sense. In the hands of a less gifted actor, it wouldn't work."

According to Rudd, Segel does something that no one else does: "He is simultaneously hilarious and creepy" and also does a great impersonation of the "Princess Bride's" good-hearted giant, Fezzik.

Segel offered a quick, demonstration, explaining, "It's how you use your tongue." The two looked at each other before dropping the obvious follow-up line: "And that's what she said. Pow!"