Mrs. Greenback is made entirely of money making her light green in color. Her design resembles feminine attributes. Being inanimate though, there are few features.
Mrs. Greenback was first created by Mr. Krabs after he got gets locked in the safe deposit box of the Bank of Bikini Bottom Bank. She is apparently his date and even enjoys a day on the beach with him. However, after the beach catches on fire, Mrs. Greenback is "eaten" by a "Money Dragon," which is actually a vacuum, and is never seen or heard from again. Actually, the whole thing was in Mr. Krabs' head, because he was running out of oxygen in the bank vault, resulting in hallucinations.