Who's the brown dinosaur in Braid?

Solution 1:

Although David Hellman did most of the art for Braid, Edmund McMillen did some early character designs including the dinosaur^[1]. You'll recognize Edmund's style from other gaming.SE favorites such as Super Meat Boy and the Binding of Isaac.

You can see the squat, tie-wearing style for Tim was kept from Edmund's early drawings, though David mentions that he redid the face for Tim. You can see variations on the Braid dino from Edmund here. Edmund didn't mention any specific inspirations from other sources^[2]; he's just a plush dino and one of his original creations for Braid.