This is a really crappy old pic but I recently moved back home and found it while unpacking.
 
So in the Roseverse, Equestria is a diverse nation of Equines and other animals. The most common citizens are Earth Ponies, Unicorn and Pegasi. However the exist many races and mixes.  
For example you can have sleek almost Arabian breeds of Earth Ponies or fluffy workhorse types. Similarly, Unicorn can be tradition [meaning they have a lion-esk tail and a beard], Earthicorns which have more sturdy frames and Yunikōn a Neighponese breed [Curved horn with a tall thin frame]  
Pegasi are no different. There are traditional, birdlike and batlike.
 
 
In the Roseverse, Scootaloo is a Bat Pony hybrid.  
This doesn’t affect her personality or demeanour. She’s still diurnal as she’s only half Bat Pony and I still have no idea what her parents are like [in adulthood they are clearly not close and she has little contact with them]
 
As an adult Scoots looks no different but she is a wee bit taller. Applebloom is the strong one, Sweetie Belle is the tallest and Scoots is a wee shortie!!
 
 
There are many other pegasi in my AU that are now bat ponies or hybrids [Like Rumble/Thunderlane, Blossomforth etc]  
They are not rare.