Celestia loves Cake. Pinkie Pie, Joe, and that mule lady were busy. Only one option to turn to, Gustave has had a crush on Celestia for a long time. He decides to slip some love potion into her cake slice, but accidentally drugs the whole cake in the process. This cake is presented by accident to a political leaders party or whatever. Fluttershy came because the rest of the EOH are busy.
Sh*tty scenario I know, came up with it in 10 seconds flat.