There is a joke that a man bought a ticket with a forged seven-dollar bill.

A woman took counterfeit money to buy breakfast,

The peddler was annoyed: "Elder sister, it's nothing if you give counterfeit money.".

That's at least a seal. Your bill is actually a painting!

To say the least, forget about this painting.

You can write a ten-dollar bill or a five-dollar bill.

You also draw a set of seven!

Let's make it seven, or at least draw a color one.

I cann't believe I used a pencil. Forget it. Black and white is good.

You can't draw with toilet paper!

Poor feel,

Even toilet paper, cut the edge with scissors.

This is torn by hand, and the raw edges are too exaggerated.

Ok, I'll put up with the burr, but you can also tear a rectangle.

This triangle is so unreasonable.

I don't know if that's what you're talking about, but there's also a joke about counterfeit money in 7 yuan:

Two counterfeiters inadvertently made counterfeit banknotes with a face value of 15 yuan, and they decided to spend them in remote mountainous areas. When they bought a 15 yuan candied haws with 0 yuan, they cried and the farmer gave them two 7-dollar ones.