From My Little Wiki
This unicorn pose has all four feet flat on the ground. Head is looking up towards the sky.
Ponies in the Powder Pose
Sweet Pocket (Prototype)
No Horn Powder Pose
As seen in this French language ad on youtube, Hasbro originally intended to have a variety of poses appear in the Dance 'n Prance set. Hasbro apparently decided fitting mechanisms to more than one pose was too hard. Instead they choose one, the Powder Pose, and then removed the horn for a few ponies to feign pose variety.