Image from the "My Little Pony Magical Gallery":https://apps.apple.com/gb/app/my-little-pony-magical-gallery/id1586149043 app, resized to the original aspect ratio of the painting.

Original description:

Hi, everypony! You’ve found another My Little Pony pic in our Magical Gallery, this time of singing superstar sensation, the pegasus Princess Pipp Petals! Meanwhile, up on the wall we’ve got ‘Frederick Rihel on Horseback’, which was painted around 1663 by Rembrandt, one of the greatest painters in the history of art. Frederick looks so calm up there, even though his horse is rearing up. That said, why the long face?! (I’m talking to Frederick, not the horse!) One of the most amazing things about this painting is that Rembrandt went ahead and painted it right on top of another painting that he had already started. You can see traces of the old painting between the horse’s legs. So, there’s actually another painting underneath this one! What do you think it’s a painting of?