Williams' widow, Susan Schneider, put on a brave face as she walked the red carpet, and later attended the star-studded after party at the American Museum of Natural History.
Meanwhile, Robin’s co-stars paid tribute to the comedian, who played Theodore Roosevelt in the trilogy.
Ben Stiller told “Extra’s” AJ Calloway, “He was a genius and an incredible person.”
Ricky Gervais added, “He couldn't have been nicer to everyone. He was always trying to make you feel good.”
He continued, “What happens is you watch Robin do his thing, and you stand back because you mustn't ruin it.”
Owen Wilson remembered being paired with Robin for the press junkets. “You know those press junkets can be kind of tedious, but when you've got Robin there who's never giving the same answer twice… it was exciting just to watch him.”
“Night at the Museum: Secret of the Tomb” opens in theaters on Dec. 19.