Well I've been thinking about this for a while and I wanted ask people what they thought Pinkie's story was about that ended with the sentence "And I said," Oatmeal, are you crazy!?".
This is my theory on what the story could possibly:
Derpy walked into Sugarcube Corner.She walked up to the counter where Pinkie was at and said "Hiya Pinkie. Um, I'm looking to buy a dozen muffins for Dinky's party."
"What kind?"Pinkie asks. Derpy answers." Oatmeal, that's Dinky's favorite." Pinkie exclaims."Oatmeal, are you crazy!?"
What do you think was Pinkie's full story?