In The Muppets' Wizard of Oz, instead of being a dog, Toto is a king prawn, rescued from Aunt Em's Diner by Dorothy since Aunt Em won't allow her to have a dog. He is one of her few friends in Kansas, and she rushes back into the trailer to rescue him during the tornado.
Once transported to Oz, however, Toto, having broken out of his tank, has enlarged, is nude, and speaks with a Spanish accent. Dorothy supplies him with costuming, and he (portrayed by Pepe the King Prawn) tries to become her agent in return.
Toto is made to look like Dorothy's pet, but doesn't get any more screen time until very late in Return to Oz. Her real pet turns out to be Billina in the long run. Despite this, he is still her official pet, since most media, including the Oz franchise, explicitly dismisses Return to Oz from canon.
Foo-Foo took on a more traditional portrayal of Toto in The Muppets Go to the Movies and "The Wizard of Foz," a comic from Muppet Magazine issue 4.