So I found this bug in 14w11b, where a mushroom on the mooshroom's back is floating. It still exists in 14w19a. I didn't post right away because I am new to the bug tracker. Unfortunately, I cannot post any pictures because I don't know how to find the screenshots I took.
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CubeTheThird
Duplicate of MC-47475.
Screenshots are located in the .minecraft/screenshots folder, which can be accessed by opening the game launcher, and pressing "Edit Profile" -> "Open Game Dir".