Adam "Ad-Rock" Horovitz stopped by The Tonight Show Starring Jimmy Fallon on his first solos appearance to promote his new film While We're Young. Instead, he talked about touring with Madonna and his original intentions to be an actor, and became friends with Fallon's other guest Will Forte. The trio also got to touch fish and other "river monsters" with River Monsters host Jeremy Wade.

Ad-Rock plays Ben Stiller's character Josh's best friend in While We're Young, directed by Noah Baumbach. Ad-Rock plays a new father who tries to bring Josh back to reality after Josh and his wife start to hang out with a 25-year-old couple constantly.

Although Ad-Rock did not really talk much about the film, he talked about wanting to be an actor when he was younger. He was on an episode of the show Equalizer, but luckily he decided that being in the Beastie Boys was better.

This is Ad-Rock's first solo Tonight Show appearance. Previously, he had always come on with his bandmates. While on the show, he felt self-conscious about how he looked.

"I should have shaved or showered or something," Horovitz said. "I'm wearing a dirty shirt. I should have worn a hat. I feel like I have a big forehead."

Fallon reminded him that Horovitz was wearing a suit originally, but decided to change into the dirty T-shirt. Then Ad-Rock mentioned off-hand that he enjoyed the gift that Fallon gave him of Uggs and other merchandise.

Will Forte, who had been sitting next to Ad-Rock, had not been given one, so he walked off stage while Fallon protested that his was in the mail, but of course he came back. Ad-Rock and Forte, who is currently starring in the TV show The Last Man on Earth, talked quietly about how much of a jerk Fallon is.

For the first time in a long time, it looked like Fallon almost did not know what was going to happen on his own show  -- but in a good way.

Ad-Rock also talked about the Beastie Boys opening for Madonna in the 1980s before their first album was even released. He said Madonna's fans really did not like them, but Madonna insisted on keeping the group on tour with her anyway.

At the end of the show, Fallon, Forte and Ad-Rock got a lesson on river monsters with Jeremy Wade, but Ad-Rock stayed far away from the action. The group was shown various dangerous, poisonous and slimy creatures. Forte decided to kiss some kind of electric fish and Fallon had to hold a creature known for eating already dead fish. Ad-Rock refused to hold any of the fish and stayed 4 feet behind the other two participants.

Watch this encounter below.