Rainbow Dash, Scootaloo's Godmother, needs to lie. If she doesn't, she could get fired from her job. Sadly, this also means lying to Scootloo. On her birthday, she wished Rainbow couldn't lie. This turns out to become a giant mess for the Pegasus. When her parents decide to take her away so she wouldn't be hurt anymore, Rainbow realizes her love for the orange filly, and how much she really cares.
((The movie "Liar, Liar" is not mine! The story, however, is!))