<Li> Raegan Revord as Missy Cooper, Sheldon's twin sister . She teases Sheldon along with Georgie but not as much . She does not share Sheldon's intelligence but is very perceptive . While she does not always get along with Sheldon, she finds in her twin brother a solid confidant and has admitted to not feel as whole without him . </Li> <Li> Jim Parsons as the voice of adult Sheldon Cooper, who narrates the series as the older, present - day version of the character . </Li> <Li> Annie Potts as Constance' Connie' Tucker, Sheldon's maternal grandmother, known to him as "Meemaw". She is very close with Mary and her grandchildren but does not think highly of George and often jokes about him . She is the most patient and understanding of Sheldon's quirks and advises Mary to trust that Sheldon will find his way . </Li> <Ul> <Li> Wyatt McClure as Billy Sparks, the son of a neighbor to the Cooper family, who is not very intelligent . </Li> <Li> Billy Gardell as Herschel Sparks, Billy's father . </Li> <Li> Melissa Peterman as Brenda Sparks, Billy's mother who works at the bowling alley frequented by Meemaw . </Li> <Li> Ryan Phuong as Tam Nguyen, Sheldon's Vietnamese - American childhood best friend and classmate . Tam is responsible for introducing Sheldon to many of his non-scientific interests, including comic books and role - playing games . </Li> <Li> Matt Hobby as Pastor Jeff Hodgkins, the upbeat pastor at the Cooper family's church . Like Mary, he has friction with Sheldon's atheism, but he challenges Sheldon to explore their line of thought through logic exercises . </Li> <Li> Valerie Mahaffey as Ms. Victoria MacElroy, Sheldon's homeroom teacher at Medford High . </Li> <Li> Rex Linn as Principal Tom Petersen, the principal of Medford High . </Li> <Li> Danielle Pinnock as Ms. Evelyn Ingram, Sheldon's math teacher at Medford High . </Li> <Li> Brian Stepanek as Mr. Hubert Givens, Sheldon's science teacher at Medford High . </Li> <Li> Doc Farrow as Assistant Coach Roy Wilkins, Sheldon's P.E. teacher and the assistant football coach at Medford High . </Li> <Li> Sarah Baker as Ms. Sheryl Hutchins, the Medford High librarian . </Li> <Li> Wallace Shawn as Dr. John Sturgis, a college physics professor who is romantically interested in Meemaw with Sheldon's encouragement . </Li> </Ul>

How many seasons of young sheldon will there be