California Grill requires collared shirts. It can be a short sleeved button down, or a polo style, but not the kind normally called a t-shirt (Hanes or whatnot)
I disagree on collared shirts (although I wish you were right). Right from the WDW website for California Grill. It says "may" and not "must" regarding collared shirts. Shown below.
At this signature dining experience, Guests are asked to adhere to the dress code.
Men may wear khakis, slacks, jeans or dress shorts and collared shirts. Sport coats are optional.
Women may wear Capri pants, skirts, dresses, jeans or dress shorts.
Not permitted are tank tops, swimsuits, swimsuit cover-ups, hats for gentlemen, cut-offs, torn clothing and t-shirts with offensive language and/or graphics.


