Distinguish the two events: Mr. Donald joined a theater group and Mr. Donald joined a theater performance.

The event where Mr. Donald joined a theater group refers to him becoming a member of an organized group of people who share a common interest in theater and take part in activities relating to the performance arts. On the other hand, the event where Mr. Donald joined a theater performance refers to him taking part or acting in an actual theatrical production or play. Both events are related to theater, but they are distinct in that the first involves joining a group, while the second refers to participating in a specific performance.