The star was accosted on Friday at the film's Moscow premiere by a frisky male reporter who tried to kiss Smith after the star graciously accepted a request for a hug.
Smith swung by the Late Show last night to tell David Letterman all about it, keeping a good sense of humor about the whole buss brouhaha...
"It was just awkward," Smith explained to the host, and elaborated on the build-up to the incident.
"He says, 'I'm you're biggest fan, can I have a hug?'" Smith recalled. "So I go to give this joker a hug, and he tries to lean in and kiss me!"
Smith said the reporter's team later tried to offer an apology. "They were like, 'Oh, no, we're sorry, you know. It's just his shtick, you know.'"
Thankfully, the star had this zinger handy: "I said, 'Well, that's why his ass got shtuck.'" Touché!