Complex sentence: In "Diane's Allergy" (1984), Diane moves into Frasier's apartment and becomes allergic to his female puppy, Pavlov, so he gives Pavlov to Sam, who calls the puppy "Diane".
Split into simpler sentences: In "Diane's Allergy" (1984), Diane moves into Frasier's apartment and becomes allergic. She believes to be allergic to Frasier's female puppy Pavlov, whom he gives to Sam, who calls the puppy "Diane".