Cranky was once more positive and enthusiastic. YES!YES!
I Knew It: Fans guessed that Pinkie Pie's "Smile Song" would be in this episode, and they were right! Granted, a bunch had also guessed the song would appear in "Baby Cakes", which was of course Jossed. This episode was just the next Pinkie episode on the list.
The Other Darrin: Rose suddenly sounds much older than in her previousspeakingroles. It seems that even if a background pony has a consistent name, they still won't necessarily have a consistent voice.
When Pinkie Pie says that her birthday isn't for another 75 days, that's only 4 days off from her birthday on a real-world calendar, as "Party of One" aired April 29th, and her birthday in-universe would be May 3rd.
To celebrate this The Hub aired a special commercial on May 3rd specifically for Pinkie's birthday. They tweeted birthday wishes too on May 3, 2013.
Additionally, if we take this episode's premiere date as the day on which everything but the Cold Open takes place, Matilda's birthday would be June 29th.