Inside, the Republican presidential candidate received a warm welcome. Cain laughed when talk show host Jimmy Kimmel asked how his day was.
"Well all things considered, I'm still alive. It got off to a rough start. We had a little surprise to show up on TV," Cain replied.
That surprise was Sharon Bialek, a single mother from Chicago who claims that Cain sexually harassed her back in 1997.
With high-powered attorney Gloria Allred by her side, Bialek went public Monday, claiming that she went to Cain for help with a job after she was let go from the National Restaurant Association.
Bialek is the fourth woman to go public with accusations that Cain has engaged in inappropriate sexual behavior while chief executive officer of the National Restaurant Association in the 1990s.
"[Cain] put his hand on my leg, under my skirt and reached for my genitals. He also grabbed my head and brought it towards his crotch. I was very, very surprised and very shocked. I said, 'What are you doing? You know I have a boyfriend, this isn't what I came here for.' He said, 'You want a job, right?'" said Bialek.
Bialek says Cain stopped when she protested. She says she told three people about the incident at the time, including her then-boyfriend, but didn't file any workplace complaints because she didn't work for Cain.
Cain dismissed Bialek's charges as more false accusations.
"My own wife said that I wouldn't do anything as silly as what that lady was talking about, because she does know me. I've been married for 43 years to the same woman, and I'm proud of it," Cain said on the late-night talk show.
Bialek says she is not asking for money and is not planning to write a book or file a lawsuit.
"I'm coming forward to give a face and a voice to those women who cannot or for whatever reasons do not wish to come forward," said Bialek Monday.
Three other women have reportedly accused Cain of sexual harassment while he was running the National Restaurant Association. The association settled claims with two of the women.
Cain's campaign issued a denial Monday. "All allegations of harassment against Mr. Cain are false," it said, adding that the recent accusations are "bogus attacks."
Cain's appearance on "Jimmy Kimmel Live!" stems in part from a pizza-related sketch Kimmel did on the former Godfather's Pizza president and chief executive about a month ago.
"I think it's a tremendous opportunity for us," said a spokesman for Cain. "Mr. Cain has said for months now that America needs a sense of humor and to the extent that he appears on shows like with Mr. Kimmel, I think he can help achieve that."
Cain also has "a couple of private events" planned for his trip to Southern California, his spokesman said.
The Associated Press and City News Service contributed to this story.