Former "Tonight Show" host Jay Leno made a cameo Monday night at his alma mater and did a surprise guest monologue for the show, when Jimmy Fallon faked a "hammy" in classic Johnny Carson style.

According to Deadline, the stunt began with Fallon starting the monologue as normal with a Bernie Sanders joke about support for President Obama. Fallon then faked pulling his hamstring and asked someone to tag in for him.

Leno appeared and quickly obliged the injured host's request. The former host came out to generous applause and broke into his own comical monologue right away. In his first bit about Hillary Clinton, Leno joked that he was surprised Ralph Nader was still alive.

One of the better jokes from Leno's set was at the expense of former Maryland governor and current Democratic presidential hopeful Martin O'Malley. Though the candidate has been in the race for the party nomination for eight months now, establishing himself as one of the earliest candidates on the ballot, O'Malley is only polling at 2 percent.

Leno capitalized on the low polling numbers, pointing out that O'Malley is "only tied with low-fat milk."

The audience loved it, giving the joke thunderous applause.

Meanwhile, Leno revived his "how bad is it" style of comedy with a series of "how bad is the economy" one-liners.

"So bad, I saw a woman on Park Avenue with real breasts and a fake Gucci bag," Leno said. "So bad, parents in Beverly Hills are being forced to raise their own children. So bad, a priest, a rabbi and a minister walked into a bar and burned it down for insurance. So bad, the Kardashians are losing their *ss."

When the monologue was over, Fallon invited Leno to stay for the remainder of the show.

Leno responded, "Can't, I'm lead guest on Colbert," before making his grand exit.

See the video of Leno's monologue below.