“An elated Pinkie Pie is planning the biggest and best "birth-iversary" party ever for Rainbow Dash, but when another party planning pony named Cheese Sandwich rides into town, plans change. Soon, everypony is so excited about Cheese Sandwich's party that they forget about Pinkie Pie, but her pride won't let her go down without an official "goof off."”
@Guest: That may be so, but the songs in this episode actually work. They not only fit the mood but they also serve in actively progressing the plot; Instead of Magical Mystery Cure, in which the songs mainly just serve as padding. Songs like this aren't bad when used in moderation, but too much padding makes it glaringly obvious that the padding (in this case, the songs) is present, pointing out the lack of actual plot.