I wasn’t originally planning for a bored expression, but staring at this pose long enough made me think of various idle animations of Sonic The Hedgehog in vaguely similar poses (minus genitals of course) so I made him look annoyed and bored. :v
 
Possible captions:  
“I said “It ain’t gonna suck itself.” ten minutes ago, what are you waiting for?”  
“Are you done staring yet?”  
“I don’t think my front hoof is supposed to bend this way.”  
“You’re the slowest painter in the world.”