This Mouse, a little guy, has a problem that he is afraid to share with anyone. He does not understand what it is or why he always feels sad , thinks bad thoughts, hardly ever has fun and sometimes feels like he's crazy. And... he is "the only one in the world to ever feel this way". Our soon to be good friend, "this mouse" has OCD, short for Obsessive Compulsive Disorder. OCD is a problem with chemicals in the brain.