Wallace Shawn is a minor character in BoJack Horseman based on the real-life actor Wallace Michael Shawn of the same name. His most prominent appearance was in One Trick Pony, in Season 1.
Wallace Shawn is a balding grey-haired human man with signs of wrinkles on his face who wears a yellow turtleneck, grey jacket, pants, and shoes.
According to the model sheets, with the horse mask, he is roughly slightly above 6 1/2 ft tall.
To portray BoJack Horseman in Mr. Peanutbutter's Hollywoo Heist, 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.
Wallace Shawn is an exaggerated version of his real-life counterpart.