Oh, I am in love with milkshakes. This branch is cute, like it's from the fifties or something, and it fits in nicely with the whole rockabilly vibe in the Plaza Midwood area.
My favorite is the Blizzard. I'm a fan of Oreos smashed up in vanilla ice cream. The staff here is always quick and friendly, and they are open late enough to make an excellent dessert spot after Penguin or Dish or whenever you find yourself in the area for dinner.
It's not quite as good as Cook-Out, but it's in the Plaza Midwood area, which is a plus, and it's got a cool vibe with the walk-up instead of the drive-through.