Like many shows that centered on a cast of teenage characters, the stars of That ’70s Show were a variety of ages in real life when the iconic sitcom premiered. Over the years, the ensemble cast of the show saw a few major changes, but for the most part it was led by a consistent young cast that included Topher Grace, Mila Kunis, Ashton Kutcher, Danny Masterson, Laura Prepon, and Wilmer Valderrama. The only major non-adult series regular to be added to the young ensemble was Josh Meyers’ Randy Pearson, who joined the cast for the eighth and final season.

https://screenrant.com/that-70s-show-cast-members-age-1998-release/