Just rewatched Sonic Rainboom in honor of Rainbow's Birthaversary today. Found a continuity/character error? Details inside.

Pinkie says she's never seen a Sonic Rainboom, but points out they're legendary. Applejack mentions Rainbow Dash is the only one that has performed it. Sonic Rainboom is, in continuity, before The Cutie Mark Chronicles. Yet, there's still an error here. Pinkie describes what it is. "When a Pegasus like Rainbow Dash gets going sooo fast... Boom! A sonic boom and a rainbow can happen all at once!"

We see later in The Cutie Mark Chronicles, the moment before and during when Pinkie notices the Sonic Rainboom. She can't claim to have never seen one if she's able to perfectly detail what occurs. Sure, Rainbow could've explained what happens, but we know Pinkie has seen one before.

Additionally, how could AJ know Dash is the only one who's performed one? This implies she knows exactly what it entails and vividly remembers seeing it as a filly. Moreover, her statement must mean Rainbow told Applejack she was the one who did that Rainboom many years ago.

This contrasts the later episode when the rest of the Mane Six recollect how they got their cutie marks and all remember the same explosion and rainbow.

Either Pinkie is lying for the sake of it, or the characters forgot Rainbow pulled off the Sonic Rainboom by the time The Cutie Mark Chronicles happens. It's fun to rewatch episodes and have certain theories and questions arise!