Why So Cereal?

What does Joker say when someone gets angry at him for not liking oats?

"Hey, why so cereal?"

Cereal
Joker
Breakfast
Food
Villain
Short jokes

Explanation

Explain Bear

Listen up, smooth-brain. The Joker's famous line is "Why so serious?" Oats are a type of cereal. "Cereal" sounds just like "serious." It is a basic pun, but I guess your two remaining brain cells needed a bear to spell it out for you.