榆树市

树 = 对 + 木 : Sheldon Shrimp cultivates a Christmas tree in the space station's bathroom. He is very happy that he found the right tree, just the one he imagined, and—in his mind—marks of the tree he imagined with a big green check mark.

市 = 亠 + 巾 : Mnemonic symbol: a supermarket.

Sherlock Holmes (sh) started a supermarket (市) in the space station's bathroom (Ø4), but all he has for sale right now are berets (亠) and towels (巾). He should have opened it at the beach!