The film was officially a test of the PhotoRealistic RenderMan software. This was the only Pixar short rendered on the RM-1, a RenderMan specific computer that was never sold to the public. As with "Luxo Jr." and "Red's Dream", it was also a chance for Lasseter to one-up his earlier efforts, taking his animation and storytelling to another level. The baby proved difficult to model and animate; "it just became an incredible burden," remembered Flip Phillips, a new member of the team at the time. In early attempts at a model of the baby's head, he appeared to have the face of a middle-aged man. The final version of the baby (known to the team as Billy) had a much-improved face with 40 separate facial muscles, but his skin had the look of plastic. When he moved, moreover, his body lacked the natural give of baby fat and his diaper had the solidity of cement—compromises made necessary by lack of time and the still-developing technology.