Tennis, anyone? - Allegedly Bogart's first line on stage in a Broadway play, but there's no evidence he ever said it, let alone as his first line, and what his first line really was is unknown.
The first play he was in was 'The Ruined Lady', for which he was the tour manager, and someone dared him to go on one night when he boasted about how easy it looked. He was given one line to say, and allegedly declared he never wanted to act again. Not sure what the actual line was though.