From PhD Comics:

And no, mad scientist doesn’t qualify as a physic costume.

Jennifer Ouellette explored some of them last year. My favourite there was suggested by Black Stacey:

Carry a conductor’s baton and wear a hula hoop around your waist and
you are a SuperConducting Supercollider for the night.

Not so exciting Schrodinger’s cat:

Doppler effect from Big Bang Thoery

There have to be more well defined, well executed, witty physics costumes!