I think what happened is that this artist was painting from his imagination, and he painted that boy with the blue pants that you can see at the bottom of the painting first.

But he really fucked up that part and the blue pants boy looked super weird, and he couldn't figure out how to fix it, so he painted another boy on top of the first boy to hide the mistakes.

But then, that boy looked pretty weird, too, so he painted a horse on top of the boy. But he painted the horse too small, so he had to have the horse lift its leg to hide at least part of the boy. But then, the horse looked pretty weird itself, so he just moved to a different part of the painting.

this is part of the Journey of the Magi on the east wall of the Magi Chapel in Florence, painted by Benozzo Gozzoli around 1459.

I'm wondering if it some sort of signal, his other hand is holding his belt weirdly, so maybe something like a gang sign that his contemporaries would understand? That or that painter wanted hum reaching for his dagger, but got the arm position wrong?

We got ourselves a real dandy here