Young Stephen Colbert, in rare video, performs improv in 1985

From time to time Stephen Colbert reminisces publicly about his crucial years at Northwestern University, notably during a 2011 commencement address and “Late Show” visits by his old classmates David Schwimmer and Dermot Mulroney. But actual video of collegiate Colbert back in the day has been scarce — until now.

Footage posted last month on YouTube offers a 15-minute look at Colbert in his formative years, paying a call to a public access cable show in Evanston called “The Friday Club” in 1985. He’s there (in a chunky cable-knit sweater and no glasses) with three teammates from No Fun Mud Piranhas, a group that represented Northwestern in an ImprovOlympic college league.

The four teammates — all white males — do an abbreviated, seven-minute improv set riffing on the audience suggestion “rain.” The 21-year-old Colbert plays an ice sculptor in one off-the-cuff scene, and then later plays him again, this time with a previously unheard Italian accent.

He also announces to the audience that rain has seeped into his shoddily stitched boots. “I have wet socks,” he declares. “I’m performing with wet socks.”

Afterward the four actors sit down for an interview with host Paul Guinan, explaining the group’s techniques and plugging upcoming gigs at the old Lake View club Crosscurrents.

It likely was Colbert’s first time on TV, says Chris Pfaff, the Piranhas founder who posted the video. Pfaff is seen leading the group during the “Friday Club” appearance and teams up with Colbert to explain the group’s name — back and forth, each speaking one word at a time.

Trey Nichols and Larry Buhl were the other Piranhas on the show. Not present: Schwimmer, who joined the team later and went on to considerable TV success of his own.