Voluntary V. Involuntary
According to Guerrero (2011), "Children cannot choose their family; rather. they are born or adopted into relationships with parents, grandparents, and other relatives."(12) Likewise, Buzz and Woody did not choose to be Andy's toys. They were adopted into his "family". So, as brothers of sorts, Woody and Buzz have an involuntary relationship. Together, they had to decide whether or not their involuntary relationship was going to be good or just plain ugly. For quite a bit of the first movie, they chose not to get along. But, voluntarily, they chose to be friends.
Self-Presentational Goals
According to Canary and Cody's research on self presentational goals, "People resemble actors on a stage, presenting themselves in the most favorable light."(13) An example of this is when Sid, the next door neighbor, pretends to be good around his parents. Sid tries to make himself seem like a really genuine guy, although the toys see differently. Also, when Sid is torturing the toys without knowing they can talk and have feelings, he is a pretty nasty guy. Then, when Sid is shown up by the toys in his backyard, Sid tries to act like a nice kid and puts himself in the most favorable light possible.
See Notes for citations and pictures S and T.