He is one of my favorite parts of this movie. I love his eccentricities.

Very good explanations. I just thought he was a lonely little boy getting love from his grandma.

valid question and helpful response. thank you both.

Often in abandonment issues, the child has trouble finding themselves again. Grandma understood, being eccentric herself, and allowed him to explore it.

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Very nicely put!

you dictated your thoughts brilliantly, i couldn't have said it better.
i love it when birdie photographs him when he is in the clown costume.

These are very good theories about his presence in the film.

yeah, actually, that does help. thanks.

My own theory is that he parallels Birdee. Both are victims of people who have abandoned them for someone or something else. Travis was left by his mother in search of an acting career in California. Birdee, as we know, was left by her husband for another woman. After Birdee's mother's funeral, Justin comforts Travis as he both mourns the loss of his Grandma, and misses his mother. Justin does the same for Birdee as she grieves.
Sorry, I'm really horrible at dictating my thoughts, or in this case writing them. I hope that all made sense.
Another idea I had was that Travis is like Birdee in that both are trying to find their own identity which is shown through his multiple costume changes, where throughout the film Birdee is establishing a new life separate of her husband by moving, getting a job and so on Maybe thats a bit of stretch, but hey, its worth a shot. I hope that helps.