How about these two niches:

1. non-vegans eating with vegans at a vegan restaurant, where eating there wasn't their choice (they were craving a burger), and so, being forced to order off this menu, will choose the most burger-like thing on the menu.

2. non-vegans eating with vegans at a non-vegan restaurant, where for whatever reason they feel the need to impress / not-offend the vegan by eating vegan food as well. (Think "first date" or "client meeting.")

In both the situations, I'd order the best vegan thing on the menu instead of nasty imitation meat.