Shawn Astin, who played the optimistic leader Mikey Walsh, was just 14 when he took on the role. Now 54, Astin has built a successful career, known for performances in “Rudy” and “Stranger Things.” Josh Brolin, portraying Mikey’s protective brother Brand at age 17, has also enjoyed a distinguished career, age 57, with notable roles in “No Country for Old Men” and as Thanos in the Marvel Cinematic Universe.