They're Buckeye Leaves from a Buckeye Tree.
And Big Nut is the newer generation of fan who's just trying to get camera time. Neutron Man (Orlas King) is the ultimate fan. Sadly he died a little while back.
I remember Archie Griffin having them spilling over to the other side of his helmet by mid-season.
We had a guy named Mad Mike in the 80s and 90s. Would walk around the crowd and beat a drum, yell and fire up the fans. Dressed in shorts and a short sleeve jersey no matter the weather. I was at the 1991 OU game (Friday after Thanksgiving) where it was raining and cold as hell. I'm sure he kept warm by downing lots of Yukon Jack. I believe he's passed on.
Now, we have the Husker Elvises. Three guys in all-red/white Elvis get-ups, pompadours and 70s sunglasses.
I like the guy who dresses up as Woody Hayes. Yes, Woody had a meltdown, but still a legend. Devaney and Ozburn are too revered here for anyone to dress up like them.