Last year and the year before, I wore my elf ears to work with normal clothes. When my hair is long enough, it covers my ears so you can't see the seams and since they have makeup on them that matches my skin tone, they can be convincing if you aren't looking to closely. I weirded so many people out, it was hilarious. "Are those your real ears?" "What?" "Your ears, they're huge!" "Well that's not a very nice thing to say."
I would wear them to work the Friday before Halloween, but nobody comes in my lab in the mornings.