That’s been photoshopped. I can tell by the pixels. 
Actually, it is odd - because mice really can flatten their bodies, and if their head can get through, the rest of them can. I suspect it was an issue of not having any purchase with the rear legs, seeing as a stick managed to push the mouse through.
Moral of the story? Line your kettle spouts with sandpaper, people! Or risk wee mousies being stuck.
