VIDEOS:
"Tell. No. Pony"
Upon learning that her sister Maud inadvertently helped Starlight Glimmer's plan to steal cutie marks, Pinkie Pie awkwardly laughs while halfheartedly suggesting they should never mention that part to any pony. She then makes a point to show she's deathly serious about it.
Example of:
Let Us Never Speak of This Again
Example of:
Forgotten First Meeting