Painting on butt cheeks isn’t exactly the easiest thing to do. These jiggle around, since they’re just layers of fat. Hence, as an artist, you would have to be precise with what you’re doing. This lady’s taking her time putting on additional décor on the guy’s left bum.
This looks pretty appropriate for the situation. When you’ve got a pair of female Easter bunnies being painted on one side of the cheek, surely you’d have to paint them in a way that expresses joy, right? After all, it’s Easter. It’s not like they’re happy just because they’re on a guy’s glutes.