At first, I was a little hesitant to eat here because of the "stoner" vibe. However, the menu has a lot of great vegetarian options, so it's definitely worth visiting if you're in the area.
In addition to being able to build your own pizza or calzone (using a variety of interesting toppings), there is a vegetarian tortilla soup, a hummus platter, soft pretzels (the dough is vegan, but some of the toppings contain dairy), a grilled tempeh sub, a teriyaki tofu sub, an avocado and provolone sub and a "capri" sandwich.
I was thrilled to find a grilled tempeh sandwich after not eating protein for my first three days in Carrollton. The menu mentions specifically that the tempeh sandwich can be made vegan but I talked to an employee and it turns out that the tofu sandwich can also be made vegan pretty easily. The soft pretzels are vegan if you get them without any butter or parmesan (you can ask for marinara to dip them in).
The food isn't gourmet but it's definitely palatable. The portions at Mellow Mushroom are generous and the prices are very reasonable.