As stunt casting goes, it’s not a bad idea at all: For 10 weeks, beginning November 3, Grammy winner Jason Mraz will play the love interest in Waitress, the Sara Bareilles musical, based on the film of the same name, that’s well into its second year on Broadway. Mraz already has recorded Doc Pomattter’s numbers on Bareilles’ own album of songs from the show, which marked her Tony-nominated Broadway debut. (The original cast album features Jessie Mueller in the title role and Drew Gehling as Dr. Pomatter.) Following Mueller’s departure from the Brooks Atkinson Theatre, Bareilles did a record-breaking stint as Jenna, the pregnant, unhappily married waitress and baker of killer pies who falls in lust with her married OB/GYN. The role is currently played by Betsy Wolfe.