Ht. Jonathan Hanson.
Update: Mark Farrell- Churchill responded with a corollary joke in the comments, too good not to share:
Werner Heisenberg gets pulled over by a traffic cop. Cop walks up to the car and says, “Sir, do you have any idea how fast you were going?” Heisenberg responds, “No…, but I can tell you exactly where I was!”
Update 2, from Peculiar:
Heisenberg gets stopped at a Border Patrol checkpoint. “Sir, the dog alerted, we’re going to have to search your vehicle.” They open the trunk. “Sir, you have a dead cat in here.” “Well sure, NOW I do!”