Young Sheldon 4x18 The Wild and Woolly World of Nonlinear Dynamics - Clips from Season 4 Episode 18 - Promo Trailer HD - Young Sheldon 4x18 "The Wild and Woolly World of Nonlinear Dynamics" Season 4 Episode 18 All Sneak Peeks (Season Finale) - Missy's first heartbreak triggers a series of events that lead the Cooper family to the brink, on the fourth season finale of YOUNG SHELDON, Thursday, May 13th on CBS.