My favorite was from episode 55: Sakura and the Sakura in Wonderland, when Chiharu and Yamazaki are in the library and he's reading a book.
"What are you reading Yamazaki-kun?" Chihiro asks as she approaches his desk.
"This," Yamazaki holds up his book to reveal the title: Aliens are Turning into Cats and are Taking Over the World.
"I've read that before," Naoko suddenly joins the conversation, her spectacles gleaming with excitement, "Do you think it's true?"
"Of course it's true!" Yamazaki emphasizes. He then goes off on a spiel on how all different animals are aliens such as dogs, keserean-peserean types, penguin types, goldfish types and so forth.
Chiharu sighs in disbelief as he continues to list the different types of alien-animals.