Pinkie Pie is baking a pie for Rainbow Dash’s 73rd Wonderbolt training session. Rainbow accepts the pie at Wonderbolts HQ, but Pinkie soon finds the pie in the dumpster instead of inside her stomach. As a matter of fact, Pinkie has never seen Rainbow eat one of her pies, she’s always been distracted (read: fall for trick of looking away from Rainbow).
Pinkie comes to the conclusion that Rainbow doesn’t like her pies and has lied about liking them. Pinkie’s attempts to catch her in the act come up fruitless until gravity exposes Rainbow Dash as a pie she throws up into the air lands on Pinkie. The truth is Rainbow Dash does not like ANY pies (which comic main series #59 will delve into).
Rainbow though the hassle was worth it because Pinkie would be crushed if she found out someone didn’t like her pies and it made her happy to see Pinkie happy. Also, she was willing to eat a “pie” she baked to make it up to Pinkie. That’s kind of the sour part of this episode. They do mention that Rainbow should be more honest with Pinkie, but her way of trying to make it up to her is as overly-complicated as her schemes to get rid of her pies.
But really, that was the only sore point, though a significant one in my opinion. Other than that, we get some very good facial expressions and Pinkie’s imagination go out of control (liked the “Evil Dash” bit). It’s just that Rainbow didn’t need to overcomplicate things in making amends with Pinkie.