My Little Pony LXXIII: Luna's Sordid Dreams? I'm Not Googling That...

[erikun]

If Chrysalis was trying to establish a foothold in Canterlot it would make sense that she would disguise herself as a higher up.

Actually, I had an idea. If Changelings are not limited to pony disguises what is stopping a Changeling from disguising itself as say, a fluffy puppy, and endearing itself to a young filly?

Size, probably. Also eating dog food.

[EDIT] Actually, the comics mentioned that changelings could only turn into a "pony" (although I'm sure there's some leeway there) but a different creature could turn any anything else... including a dog. So no dogs for changelings, at least by strict canon.