Looking for a Chatbot for interactive theatre piece

I’m creating a piece of interactive online theatre this summer, and one of the elements will be where the audience gets to interact with a chatbot as a part of the narrative. They’ll think they’re talking to a character in the show, when in reality, it’s the chatbot.

Do you know of any easy-to-set-up bots that could be used? Ideally, I’d love to find something that passes the Turing Test, that can have customized writing, and is cheap/free.