One thing that I've been thinking about lately is the role of the audience in wrestling, and the notion that the audience might be like a member of the performance himself.
In watching Kaufman's shtick of goading women from the audience into the ring and beating them, I noticed a lot of similarities to Calvert's shtick (from the Williams reading), where he would encourage local farm boys and the like to get into the ring and try wrestling him. Thinking back further to many of the videos we watched in which the wrestler addresses the audience ("You bunch of pencil-necked geeks!!"), I think that what Calvert and Kaufman were doing was a sort of idealized form of what these other wrestlers are doing.
So what are they doing, you ask?
I think what it comes down to is giving the fan, who might not be in the best physical shape, the opportunity to momentarily see themselves or fantasize about actually being in the ring fighting someone.
In the case of Calvert, we have an anecdote where a boy insults him, Calvert challenges him, and then he runs back to his seat and laughs with his friends. Now in a normal fight, the boy would be a coward, but somehow, by virtue of the wrestling situation he gets a chance to flirt with the fantasy of being able to challenge this wrestler, and then safely run back to his seat.
Basically, the most obvious role of involving the audience in the performance is to create emotional investment. However, I think one of the less obvious (but equally important) roles of involving the audience is to create a sort of fantasy that they are, or could be, part of a physical fight like that themselves.
I think this also accounts well for the fact that wrestling fans seem to be somewhat aware that they are performing as well. If all you wanted was emotional investment from the audience, then what's the advantage of letting them know it is fake? If, however, you want the audience to join in on the fantasy, then letting them know it is fake keeps them feeling safe.
In essence, they can "wrestle" without getting hurt.
Getting back to Calvert and Kaufman...
Now, by actually bringing audience members into the ring, I think Calvert and Kaufman capitlize on the ability to create this relationship with the audience by further blurring the lines between who is an audience member and who is a performer, thus making the fantasy far more real feeling for the audience, while still keeping things at a safe distance.
A part of me wonders if Kaufman's history as a big wrestling fan, who fantasized about being wrestler, yet obviously never had the physique to be one, might have given him a strong intuition for the audience's desire to be involved in the wrestling match and feel like a wrestler themselves. In a way, Kaufman seems to me like an audience member who went out of control and managed to take over a ring somehow.