I didn't use an erase for that creature at all, just (sloppy) hatching lines XD but I see what you mean and I DO do that sometimes - use an eraser to make the edges of my shading smooth, it's a nice technique! ^^ (thanks again for the compliments :\3)
Awesome detail on the creature thing! Also a perfectly natural playing-it-cool reaction from Trixie. I guess her defeats at Twilight's hooves may have taught her how to properly deal with drama when her show goes wrong.