There are two facts that will aid your appreciation of The Drowsy Chaperone.
Fact the first: Man in Chair isn't imagining the whole thing. When you love a work of art so much that it's become an integral part of who you are, revisiting said work of art results in complete immersion in it, and the outside world fades away.
Fact the second: Drowsy doesn't mean "sleepy," it's an old slang term for "drunk."
So, instead of getting drowsy while listening to Hear Nothing See Nothing Say Nothing for the billionth time tonight, go see this.