Jimmy Fallon did his best Joey Chestnut impression during last night's Rangers playoff game in NYC ... the late-night talk show host dunked his hot dog -- bun and all -- in his beer before devouring both, and spilling everywhere!
'The Tonight Show' host was in the building for game 5 of the Conference Finals game between the NYR and Tampa Bay Lightning ... when Fallon found himself on the big screen at Madison Square Garden, hot dog and beer in hand.
Fallon, a NY native, has clearly seen a Nathan's hot dog eating competition or two in his time .