CHRIS BROWN / RIHANNA hookups are like the BIGFOOT of celebrity hookups. People keep claiming they've seen them . . . but nobody's got proof.
--The latest unsubstantiated "eyewitness accounts" come from the Griffin nightclub in New York City on Monday night. Rihanna and Chris reportedly arrived separately, but Chris immediately moved over to Rihanna's table.
--A source says they started flirting . . . then Chris took off his shirt and started dancing on the table. Soon the two of them were dancing together and kissing passionately.
--From there, they hit the VIP bathroom together, where they spent about a half hour while security goons stood outside the door. Chris was the first one out, with "a smile on his face." Then Rihanna came out looking, quote, "disheveled".
--If this offers any further proof for you, Chris' girlfriend Karrueche Tran Tweeted this on Monday . . . quote, "There's a difference between a man and a boy. I prefer men."