Luke Perry on '90210,' 'Riverdale' + Working to Fight Colorectal Cancer with His Childhood BFF

Luke Perry stopped by to chat with Rach about his new CW show ‘Riverdale,’ reminisce about ‘Beverly Hills, 90210’ and bring attention to a deeply personal cause: the fight against colorectal cancer.

On the seemingly everlasting popularity of his hit ‘90s show “Beverly Hills, 90210,” Luke says, “I am kinda surprised by the young teenagers who catch it in reruns. They find stories that are 20-something-years-old compelling.”

He jokes, “I was 23 when we started and like 63 when we finished, something like that.”

WATCH: 3 Chic and Affordable DIY Flower Arrangements for Spring from ‘90210’ Star Tori Spelling

Now he’s playing the dad to a teenage character on “Riverdale,” which takes the Archie comics and goes someplace significantly darker. “This [reimagining] is dark and wicked. There’s a mystery, first thing in the pilot, somebody gets killed.” And it’s not a mystery that gets solved quickly, Luke teases, “We finished the season and I still don’t know who did it.”

On top of being excited for his new series, Luke has another project that he’s extremely passionate about -- the fight against colorectal cancer.

WATCH: A Woman Who Beat Cancer Gets a Makeover

He got involved after the wife of his best friend since third grade (see adorable childhood pic in the video below) got stage 3 colon cancer -- and beat it. “There are over a million survivors of this disease out there and we’re hoping to add a lot more to that list,” he says.

March is Colon Cancer Awareness Month, and Luke reveals a super-easy way you can help in the fight: Take a “strongarm selfie” (of you flexing) and post it to social media using the hashtag #StrongArmSelfie and tagging @FightCRC. Each post, retweet or share of a #StrongArmSelfie sends $1 to Fight Colorectal Cancer.

WATCH: Rach Finally Gets to Meet the Actor She’s Had a Crush on for Decades

That wasn’t all we talked about with Luke -- we gave our audience members a chance to quiz him, and he revealed the first big purchase he made after making it big (it wasn’t for him!), his favorite thing about being famous (this will make you go.. awwww), and one of the most outrageous ways he ever escaped a fan encounter (hint -- it involves hiding under a pile of clothes and boxes). Watch the video below for his answers.