He appears in Season 1's One Trick Pony.
The movie actually goes through several wacky changes, and the finished product isn't even a movie, it's a gift basket.
Wallace Shawn is a balding grey-haired middle-aged man with signs of wrinkles on his face who wears a yellow turtleneck, grey jacket, pants, and shoes.
To portray BoJack Horseman he is seen wearing a horse head mask with a cutout for his face, an unbuttoned gray jacket with a blue sweater underneath, cyan blue jeans, and red and white sneakers the same outfit that is BoJack's everyday attire.
- The real life actor Wallace Shawn is best known for roles such as Vizzini in the movie The Princess Bride or Rex in the Toy Story franchise.