Two giants of comedy walk into a Patagonia store, and what comes out? Dye job advice.

Robin Williams met up with pal Whoopi Goldberg in SoHo last night, and they did a little shopping with Robin's daughter Zelda -- and not much else. Whoopi seemed totally whupped after a long day, and packed it in early.

But even more startling was when Whoop noticed our photog's newly blackened hair, and told him to go back to his natural blond. This, from someone who has looked exactly the same since 1982.