When discussing George Bailey's background with Clarence they say his uncle has the IQ of a rabbit.
In Potter's office discussing the Potter's Field location the man said he used to hunt rabbits back in the day.
When they march the two dollar bills back to the bank safe after the run on the bank they want the money to breed like rabbits.
And of course the white rabbits in their rabbit hutch tied onto the back of Mr. Martini's truck when he is moving out of the slums into the new home in Baileyville.