Foil
Character Role Analysis
Stu
A foil is a character that provides contrast to another character. In other words, by comparing the differences and similarities of this character to another character, we can better understand one or both of them.
When we first meet Stu, he serves just this role for Mannie and all of Luna society. Since Stu is an earthworm, he doesn't understand Loonie customs and traditions. This lack of knowledge almost gets him killed when he grabs a Luna woman by the waist and attempts to kiss her. Luckily for him, Mannie serves as judge in the makeshift trial that follows, and Stu gets off with only a fine of fifty bucks.
At the taproom, we really see foiled Stu at work. Unlike Mannie, who sees Luna's society is perfectly natural, Stu feels the place is "Looking Glass Land" (11.112). Like Alice, he can't make sense from the seeming nonsense around him.
The advantage to Stu's confusion is that it allows Mannie to explain several aspects of Luna society to him. These include TANSTAAFL (11.100), the lack of written laws (11.114), and how and why women are treated on Luna (11.116-117). In turn, this explains Luna society to us, the readers, and as a bonus, we get to really understand Mannie's take on Luna society in the process.