I think they steal each other

Jim Douglas:

We've lost our car, and we'd like to know if you've seen it by any chance. Diane Darcy:
Who cares about your silly Volkswagen? My Lancia has been stolen! Waiter:
[points to Diane]
Uh, your car. [then points over to Jim and Wheely] Waiter:
And your car. Jim Douglas:
Yes. Waiter:
I saw them both. Diane Darcy:
Then you saw who stole them? Waiter:
You would not believe this. I would not believe this. No one would believe this. Jim Douglas:
What? Waiter:
I think they steal each other