The Prince and the Pauper is a novella written by Mark Twain. You can read it on Project Gutenberg for free.
It was adapted into a musical/comedy switching females for the protagonists; The Princess and the Pauper was adapted/written by Patricia Sternberg with music and lyrics by Matthew Granovetter. If you want to purchase the rights of production for this two-act play, contact Dramatic Publishing.
In October, 1989, Curtain Call (Kokomo Civic Theatre for Children)* performed this play at what was then known as Kokomo High School Downtown Auditorium (Kokomo, Indiana).
The original program:
Kokomo Tribune, October 5, 1989: “Faunce making directorial debut”:
Kokomo Tribune, October 6, 1989: “KHS downtown auditorium is site of children’s play”:
Kokomo Tribune, October 12, 1989: “Princess and the Pauper is a real family affair”:
Kokomo Tribune, October 13, 1989: “Play pulls off real switcheroo” by Ken Ford
* Curtain Call is now separated from Kokomo Civic Theatre). They are now simply Curtain Call Theatre for Children. You can follow them on Facebook. (You can also follow them on Twitter @KokomoCurtainCa but they haven’t updated their Twitter feed since 2015 so, maybe, skip that.)