When the cautious elephant Gerald and optimistic Piggie get invited to a party, they set out on a vaudevillian adventure that explores the meaning of friendship. This is the plot of the children’s musical Elephant and Piggie’s “We Are in a Play.” See it when Sixth Street Playhouse players perform at the Charles M. Schulz Museum in Santa Rosa. Shows will be held at 10 a.m. and 1 p.m., September 16–17 and September 23–24. Tickets are $34 and may be purchased at tinyurl.com/585wnkuj.