Should've been called Look Who's Hawking, that's my only criticism.
or
1,622. One to tell the original joke, and the rest to submit give some minor variation of it! For example:
or
Fish and ships.
or
They turn from notating nuclear spins to notating unclear puns.
or
When it came time to pay, the skunk didn't have a scent, the deer didn't have a buck so they put the meal on the duck's bill.
or