Chaplin was a great fan of boxing and often attended matches. He delighted in receiving prize fighters at his studios, be they light or heavyweight champions, and they presumably loved clowning around with him. His own performance in the boxing match scene in City Lights still has audiences in stitches.
The boxing poster and the sign offering money to enter a competition on The Gold Rush set makes one wonder if Chaplin may not first have thought of the City Lights boxing match scene for The Gold Rush.
In an outtake from The Circus, the tramp arranges with a boxer - whose fight we see advertised on the café wall - to allow him to knock him down in order to impress Merna. Unfortunately he hits the boxer's twin brother, who is not in on the joke, and lays Charlie flat. Merna continues to have eyes only for Rex.