Are shorts and a T-shirt appropriate at shows (specifically Mystere) or do people bring more casual/dressy clothes to wear?

not really.People tend to dress a tiny bit more for these shows,especially considering the cost of tickets, they sort of treat it as a "nicer" form of entertainment.Casual dressy is good,slacks and a polo shirt.A nice top and slacks/skirt.

Most everyone in the show we were at were dressier than that--more business casual type clothing than shorts and t-shirts.

I wore a black skirt and a black boat neck silk top.My husband wore a pale blue shirt and black trousers with a black jacket,since we had dinner at Renoir the same night.

When I saw it, most people were in jeans

really?? jeans?
I have been a couple of times,once on holiday,once on business.Most people were dressed better than in jeans.

What and where is Mystere??????

yyy

It's a Mysterey!

Mystere is a Cirque de Soleil show at the Mirage in Las Vegas

Wear anything - it's Vegas. No one cares!

When Bellagio owned the rights to "O" there was a dress code, collared shirts and jeans discouraged.
Now that MGM owns Bellagio, they don't seem to care.
I'm sure they're even less discriminating with Mystere.
One more example of how MGM is 'mediocritizing' the best of Las Vegas.

Wrong, Marvin, it's not MGM, but people like Carolyn above that are causing this problem. When masses of the public feel that you should be able to dress any way you want because "no one cares" the standards become lower. Slobs like Carolyn demand no dress codes and if places want to stay in business they need to lower their standards to those of the outspoken slobs.

Khakis and a golf shirt...ladies...sun dress or the like....casual, but not jean or short casual.