Something always bothers me about these kinds of infiltrations. Wild Shape is a relatively low level spell. And while most NPC's are essentially level 0 with no magic, it should at least be common knowledge in their world that the spell exists and MANY people have access to it.

So why would the guards not be suspicious of an animal? For that matter, why do the guards not have someone constantly using detect magic? Wild Shape is far from the only magic that can be used for infiltration, seems like common sense to constantly scan for magic around an area you are trying to keep secure. I just feel like too often, DMs treat their NPCs, especially guards, as if they have zero knowledge of magic or the world they live in.