After Twilight’s encounter with the face changers, she ventured home bringing with her a couple of her new ‘friends’ on her body.
With a spell the guards were quick to determine that Twilight wasn’t a changeling, but failed to realize she was carrying them around.
If there was anything suspicious in the bag the guards would’ve stopped her, it’s a decoy, the face changers are hiding on her body, if you notice where the spell fails to detect her ;^)
It’s eggs, isn’t it?