This, precisely.
If you've ever done any Broadway-style theater work, you know that they toss seemingly random keys at you on a continual basis. Here's an example, from a musical produced by a well-known children's entertainment company with a rodent as a mascot. We were playing along just fine then turned the page and found this key signature:
View attachment 336
Yeah, I chuffed it at the read-through. It's not hard to play, but what sort of sadistic copy editor decided to score it in Cb instead of B?