Currency

Currency is an item used throughout BFDI. The currency is equivalent to that of U.S. money. It consists of coins and dollars.

The Box of Paper Slips also seems to hold value. You can write the desired amount of money on the front of the slip, and it instantly gains value.

Coverage
In "Sweet Tooth", Pen and Eraser want to buy cakes from Leafy for the challenge. Leafy charges $5 per cake, but Pen only has $8, which can only buy one cake. He finds $1.99 on the ground, which is still one cent short. Pen and Eraser then go to find Coiny to use him to buy another cake.

The Box of Paper Slips were introduced in an ad by Yellow Face in "Crybaby". They were used by Pen and Leafy in "Vomitaco" and "Return of the Hang Glider" respectively.

Nickels were used as a Cake at Stake prize in "Vomitaco".

In "The Long-lost Yoyle City", Pin and Needle put Coiny and Nickel in close contact, which causes an explosion of coins and dollars to rain from the sky. The money is stored in a giant bag offscreen, and Spongy is forced to carry it during the challenge.

Pennies can be seen throughout BFB in Cloudy's collection.

List of known currencies

 * $0 bill (seen in Coiny & Nickel's explosion)
 * Coiny (1 cent coin)
 * Nickel (5 cent coin)
 * $1 bill
 * $1.99 bill
 * $5 bill (seen in Coiny & Nickel's explosion)
 * $8 bill
 * $10 bill (seen in Coiny & Nickel's explosion)
 * $50 bill (seen in Coiny & Nickel's explosion)
 * $100 bill (seen in Coiny & Nickel's explosion)
 * Box of Paper Slips (debatable)