You choose door #1, and walk through. As you do, the door slams shut behind you. As soon as the door slams shut, you feel the familiar tingle of hair growing along your arms. Gray hair poking out everywhere, all up and down your arms. Your arms extend outwards, growing longer. As this happens, your fingers get that familiar tighetening feel again, as they get stiff. They begin to ball up into a fist and start to disappear as your hands are covered in the hard black hooves that they are.
Your elbows twist around, as your arms are now the fully-grown forelegs of a donkey; unable to grasp anything ever again.