Selling a movie script to Disney is difficult, but not impossible. Because Disney only accepts scripts that are submitted through agents, you must first land professional representation to get your script considered by Disney.
Finding an Agent
Entering and winning screenwriting competitions is one way to get the attention of an agent. The definitive source for competition listings is Moviebytes.com. A list of agencies to query with your winning script can be found at the Writer's Guild of America, West website. An agent will sign you based on the perceived marketability of your screenplay.
Submitting Your Script To Disney
Walt Disney Studios Motion Pictures Group includes Marvel, Pixar, Touchstone and Walt Disney Animation Studios. These studios produce a wide variety of films in all genres. Your agent will submit your script to the development department of the studio that seems the best fit for your writing. Your script will then be screened by a studio reader who will summarize your script and make a recommendation to consider or reject your script. A favorable read could result in the studio optioning your screenplay for further development, or purchasing it outright.