For those of you who don't care to watch the build up, just skip ahead to 8:50
In order to get this ending, you must play the game between 11 PM and 6 AM. There are couple of steps to achieve this (unlucky) ending:
1.- Immediately getting the invitations from pinkie pie, talk to everypony (Including animals and Pinkie Pie) before helping Applejack at baking muffins.
2.- Talk to Applejack and help her baking muffins. Choose all ingredients from the left side.
3.- Then, go back and talk to Derpy (the gray colored pony at the beginning). Doing this, you will be able to invite her to the party.
4. Next, talk to everypony and animals again (except Pinkie Pie) and make sure you completely finish each conversation (They should be saying something like: "see at the party", "Bye", "Thanks", etc.)
5. Finally, go to where Zecora is. If you fulfill correctly all steps, especially step # 4, you will be getting this ending.