Final answer:
The group of teenagers would most appropriately be labeled as a reference group.
Step-by-step explanation:
The most appropriate label for the group of teenagers who share common interests and watched a tape of The Phantom of the Opera together would be reference group. A reference group is a group of people with whom individuals identify and whose behavior, values, and attitudes they adopt as a standard. In this situation, the teenagers are brought together by their common interest in theater, and they can look to each other as a reference for their theater-related preferences and actions.