[p1mrx]

Well, the Drop can take the bills back to the bank. "The corners fell off. Can I have some fresh ones?"

[steevdave]

But they can't use that specific one again, it doesn't matter if they take the bill to a bank and get new ones, because the serial numbers won't be the same.

[inlined]

I doubt a Drop cares enough about $1 to repeatedly engage in suspicious behavior with a bank

[p1mrx]

That's the joke.