Young Sheldon Kids, Then and Now: See How Much Sheldon, Missy and Georgie Have Grown Since Season 1

Thursday’s Young Sheldon (CBS, 8/7c) marks the start of the Big Bang Theory spinoff’s farewell run — and in honor of the final season premiere, TVLine is looking back at how the Cooper children (played by Iain Armitage, Raegan Revord and Montana Jordan) have grown from precocious kiddos to young adults in the blink of an eye.

In the Season 7 opener, titled “A Weiner Schnitzel and Underwear in a Tree,” news of the tornado that swept through Medford at the end of Season 6 reaches Sheldon and Mary in Germany. Also, with the Cooper house in chaos, Missy steps up

SHELDON COOPER

Iain Armitage, 15, was eight-years-old when he was cast as the pint-sized genius. Prior to playing the younger version of Jim Parsons’ Big Bang Theory character, he was best known for his role as Ziggy on HBO’s Big Little Lies.

MISSY COOPER

Raegan Revord, 16, was nine-years-old when she made her debut as Sheldon’s sassy twin sister Missy. The role was originated by Courtney Henggeler (Cobra Kai) in a Season 1 episode of The Big Bang Theory.

GEORGIE COOPER

Montana Jordan, 20, was 14-years-old when he first appeared as Sheldon and Missy’s older brother. Unlike his TV siblings, Jordan had the honor of originating the role of Mary and George’s oldest son, who had not been seen on Big Bang. The mothership eventually cast Jerry O’Connell to fill the part.

BILLY SPARKS

Sheldon spoke of his childhood bully in Seasons 3 and 5 of the mothership. Wyatt McClure, 15, was eight-years-old when the character made his on-screen debut in the Young Sheldon pilot and taunted Sheldon with his pet chicken Mathilda. Since then, however, Billy has been portrayed as more of a nuisance than a tormentor, and hasn’t given the future physicist reason to add him to his all-time enemies list… yet.