In Firefly Lane, Heigl co-stars opposite Sarah Chalke as best friends Tully and Kate, whose best friendship spans three decades. Adapted from Kristin Hannah's novel, the series charts the unlikely duo when their friendship starts at 14 years old. While Tully is brash and bold, Kate is the shy girl you never notice. But when a tragedy brings them together, they're bonded for life and inseparable best friends. Together, they experience 30 years of ups and downs -- triumphs and disappointments, heartbreak and joy and a love triangle that threatens their friendship.

For Heigl and Chalke, getting to revisit the '80s was one of the joys of being a part of Firefly Lane. 

"It was one of the many big draws for me with this project, like, 'Ooo, that's gonna be so fun.' And it was," the 42-year-old actress told ET's Rachel Smith. "I spent weeks putting together my vision board of what I thought Tully's '80s vibe was gonna be like, what her hair should be like, what her makeup should be like and it was just so fun and creative to dive back into that decade. It's wildly different than anything really."

"It was the best. It was my favorite part. We had the best time. Katie and I in the makeup trailer going, 'Wait, more hairspray, less hairspray, more earrings, blue shadow, more eyeliner!,'" added Chalke. "I have a huge soft spot for the '80s in my heart and I have a full '80s drawer over there of dress-up clothes for my kids, many of which are from the actual '80s. It was one of my favorite eras -- the music, the earrings, all of it.

The shoulder pads! It was a blast and when you put on those clothes, partly because we were quite young in the '80s, you feel that. It's a whole other energy. It's like putting on this whole other body and you kinda move differently and we were just more jumpy and [more] energy."