Bugs uses a prop to simulate a disaster for Crusher (here, a broken bone) and then shows up as someone who can help (a doctor)... but doesn't, really. This gag would be repeated a few years later in Bunny Hugged, with a slightly different angle.
First time an adversary ties Bugs to the railroad tracks instead of the other way round.
Second time voice actor Billy Bletcher uses his voice in a Bugs Bunny cartoon, and first and last time he voices Crusher.
First appearance of Crusher and second time Bugs takes on an adversary that's bigger than he is.
Boxing and wrestling were popular spectator activities in the postwar years, and were made so by the advent of a new technology, television. Early TV lineups included live local broadcasts of matches, in glorious black and white.