The dancer is a woman wearing a birthday/sweets-schemed costume. She is wearing a pink and sky blue top with sprinkles, a yellow and pink layered skirt, yellow polka-dot stockings with pink cupcake prints, and blue high heeled boots. She has long marigold hair tied in a ponytail braid and is wearing a floral wreath made of teddy bears and button flowers. She is wearing very heavy makeup consisting of blusher and eyeliner.
World Dance Floor VIP
The dancer is the performer of the classic routine, Aurélie Sériné. She is wearing a white bralette with a sweatshirt tied around her waist. She is also wearing waist high black pants with white sneakers.
The background has a pastel scheme. There are also pictures of cake and confectionery appearing. The cake reads "Birthday". It is supposed to give the dance a birthday feel. You can see many macaroons around and you can also see them with candles lit.
There are 5 Gold Moves in the Classic routine:
Gold Moves 1, 3, 4, and 5: Throw both of your arms up in the air while you lift up your right leg. Gold Move 2: Jump up with your legs fully up and hold both hands out as if you were confused.
Gold Moves 1, 3, 4, and 5
Gold Moves 1, 3, 4, and 5 in-game
Gold Move 2
Gold Move 2 in-game
There are 2 Gold Moves in the Mashup, both of which are the same:
Both Gold Moves: Open your arms. (Part Of Me) (Note)
Just Dance 2015 came out in October, either on October 21 or 23, just days before Katy Perry’s birthday on October 25.
The song was revealed in Just Dance 2015ESRB's rating summary. The following three lines are referenced as suggestive:
"Pop your Pérignon"
"So let me get you/In your birthday suit"
"Boy when you’re with me/I’ll give you a taste"
Unlike other dancers with makeup, this coach’s makeup is clearly visible.
This can be seen again on Into the Unknown, which the performer of the song also did.
The coach’s skirt sometimes gets in the way.
The dancer lip syncs "Happy Birthday" every time the line is sung.
When unlocking the avatar for this song after playing it, the lipstick is absent. However, when one looks at it in the Avatar Shop, the lipstick appears.
This also happens with Cool For The Summer’s avatar on seventh generation console versions of Just Dance 2016, as the collar is purple when unlocking it, while in the avatar shop, the avatar has a golden collar with spikes.
There was a VIP on the World Dance Floor named Aurélie during most of November 2014. Players could dance with her while this song was played on the World Dance Floor. As of January 2016, it came back.
In the preview video, the arrows for the pictograms were dark pink, despite the glove being red.
This song won in the Favorite Choreo category on the second Just Dance Awards. 
In some Beta gameplay snapshots, the coach appears to have a blue glow instead of a solid border like in the final version.
In others, the coach’s outline is orange instead of blue.