Denis Leary's third annual Bash for New York's Bravest, benefiting New York City firefighters, got an unexpected charge of electricity when Robin Williams made a late entrance with all three children in tow, reports PEOPLE.

"I'm here on a whim," said the comedian, 51. "Also, I think it's good for me to offer up something for the auction because they have to still raise money for the families (of the firefighters who died on Sept. 11, 2001). Even though they raised millions of dollars, not all of it got distributed very well."

As promised, Williams took to the makeshift stage during Monday's live auction and announced that he was "donating" a dinner in New York City with him and his wife to the highest bidder. When two people engaged in a bidding war, Williams announced that he'd instead give two dinners -- one to the bidder of $17,000, and another to an $18,000 bidder.

All told, the auction raised hundreds of thousands of dollars for the cause and attracted both celebrities and firefighters in droves. Other attendees included Kiefer Sutherland, Steve Buscemi, Penny Marshall, Edie Falco and Stanley Tucci, John McEnroe, Colin Quinn, and "That '70s Show" cast members Laura Prepon, Danny Masterson and Wilmer Valderrama.

The event raised money for the Leary Firefighters Foundation, a charity the fast-talking comedian started in 2000 to benefit firefighters in his hometown of Worcester, Mass. The foundation has since grown and has supported firefighters everywhere, particularly in New York City since Sept. 11.

Besides Williams's offering, Tom Cruise (who did not attend the event) offered two lucky people a chance to accompany him on the red carpet for the Los Angeles premiere of his newest film, "The Last Samurai." That went for $10,000. A similar package for the New York premiere fetched $15,000.

Kiefer Sutherland also got onstage and auctioned off a walk-on part on his FOX hit "24," as well as a personal tour of show's set in L.A. That offer beat Cruise's -- and went for $20,000.