Cher Gives Jimmy Fallon the Full 'Moonstruck' Slap, Performs with 'Cher Show' Broadway Cast

Jimmy Fallon was in the presence of greatness and he knew it as Cher totally crashed "The Tonight Show" Monday night.

The iconic singer was all over the broadcast, showing up on the couch, crashing the musical number and even joining Jimmy Fallon for his opening monologue. But apparently, it's possible for there to be too much of Fallon's signature gushing over celebrities.

Cher was more than happy to walk out with a beaming Jimmy to kick off his show, and it certainly did the job of getting the audience all fired up even before he'd told his first monologue joke.

"It's me," she said sweetly to the raucous response from the studio audience.

And then the gushing began. "Thank you, thank you, thank you for walking out with me," Jimmy said enthusiastically. "You are a legend, you are an inspiration."

"Yes," Cher calmly agreed.

"And I am honored to be standing next to you. I really am," he said sincerely.

After a beat, Cher replied, "As you should be."

Jimmy then asked her, "Yeah, is there, uh, anything you'd like to say to me?"

"No, I'm good."

There was only a slight pause before Fallon again began gushing over the legend, touting her decades-spanning career covering music, television, movies and now Broadway with "The Cher Show." He even started gushing about her being an Oscar-winning actress for her work in "Moonstruck."

At this point, it was pretty obvious where he was going, as he was just motormouth praising her, but it was still worth it when she hauled off and slapped him -- twice -- before delivering one of her most famous lines, "Snap out of it!"

Later, the singer surprised Fallon by crashing a performance of "I Got You, Babe" by her Broadway stars Jarrod Spector and Micaela Diamond. After letting Micaela sing a few lines of the duet she first performed with her then-husband Sonny Bono, Cher stepped out from behind stage and took over.

And if you think for a moment that she still isn't absolutely fabulous and gorgeous and hilarious and an absolute entertainer, well you clearly haven't been following the ageless wonder's career.

That's what makes it even crazier to imagine that the Cher is too shy and uncomfortable to sing karaoke, telling Jimmy, "I get embarrassed to sing in front of strange people."

Jimmy, understandably, was more than a little confused by this. "What are you talking about? At a live concert there's gotta be somebody you don't know."

"It's not the same," she argued, sharing how she was even too shy to sing in front of Sonny at home when he was trying to teach her the sing she had no problem singing on stage that night.

In fact, she was so uncomfortable singing "I Got You, Babe" when Sonny woke her up in the middle of the night to introduce her to it that she told him it wasn't a very good song and just went back to bed.

"It was really terrible, I was so shy," Cher said. And it was precisely because people didn't know or expect this about her that she put it into the Broadway show.

"If people think they know you and you know they don't, then you've got to put in those unattractive parts," she explained. "Or those parts that hit too close to home." She even confessed that there are parts of the musical that still bring her to tears every time she sees them, "Even though I know it's coming."

As Fallon pointed out, the Tonys this year will be a huge deal for Cher and awards show fans. If "The Cher Show" can nab an award, that will catapult Cher into the elusive EGOT category, as she's already won at the Emmys, Grammys and Oscars. And yes, it's a big deal to her, too.

Finally, as she'd already opened up on the couch, sang and even slapped him, Jimmy invited Cher to join him for a game of "Lip Sync Karaoke," with a Cher twist.

They'd be lip-syncing to one of her most famous songs, "Believe," but it wouldn't be her vocals they'd be performing to. Instead, they'd be lip-syncing to random people singing karaoke versions of "Believe." So, you know, really great renditions of the dance club classic.

"Can we dim the lights please," Jimmy said, trying to set the mood.

"Can we turn them all the way off," Cher offered, admitting she was a little terrified to be doing this.

Honestly, this starts off a little painful and awkward, but once Cher and Jimmy really get into the ridiculousness and awfulness of the voices they're hearing it starts to get good, and by the end it's downright hilarious. See if you can keep a straight face through the whole video below:

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