From the artist and a friend:  
“I like to imagine his cock (which is small) is locked up in there with a vibrator on it for some cagebuzzing.  
And that Cadance either did it all, or she’s about to walk in on him unexpectedly.  
Just as he’s about to cum.  
And then she patronizes him and makes him completely embarrassed about his situation.  
Telling him its perfectly okay, she wouldn’t dream of denying him the chance to go ‘number 3’ in his diaper, if he clearly prefers that to her marehood.  
And then he hits that point of no return, bucking his hips and whimpering as he finally goes over the edge.  
As she coos and rubs his back, talking down to him and telling him she’ll change him…later. Just because he’s a prince(ess) doesn’t mean he can waste a perfectly good diaper. What’s that? Yes, Twilight is still coming over for dinner, so?”