Simpsons: Season 9, episode 14
If you have the time, this entire episode is a nice illustration of group dynamics. I found it particularly useful as an illustration of group roles for a group communication class. The kids are involved in a bus accident while on a field trip that strands them alone on an island in a parody of “The Lord of the Flies.” Each group member steps into clear group roles, some are helpful to the group goals and some are not. It could also be used as an in-class activity — give the students a list of group roles and have then work in groups to define which character is playing which role.
Photo courtesy of Simpsons Wiki.