Commission for a friend's young daughter. Her favorite character in the show is our bestest friend Pinkie Pie, and she wants to be an artists when she grows up. So, I cast around in my head for an interesting way to connect the two. Pinkie and Cubism just makes sense.
EDIT: It had been bothering me for a while that Pinkie was not as pink as she ought to be. I thought that it was my monitor (or I was going blind), but it turns out that my original reference was desaturated slightly. So, I went in and corrected that, brought up the overall brightness a tad to compensate and fixed some problem areas while I was at it. I hope you find the changes worth your while.
An interesting note: while playing with the saturation, I discovered that Fluttershy's main two colors share the exact same value level (which is funny for the color theorists out there). Of course, the pony with the highest contrast is the luminous Rarity.
Painted in Photoshop.
Approximate time: 18 hours