The WSU library has some pretty cool archive football footage, much of which has been uploaded to YouTube for the benefit of fans everywhere. Buried within one of those clips, if you fast forward to 23:20 of WSU's 1970 game against Stanford, is this:
That would be a fan climbing down out of the stands to try and stop a Stanford running back from scoring. There is so much to love here!
Note the form tackle. This guy has obviously played football before and thought to himself, "Screw this WSU defense that can't stop anyone -- I could totally tackle those guys!"
Note how slow the police are to react. If you needed confirmation beyond the grainy video that this was 1970 and not 2014.
Note how nobody who actually is on the field playing the game even react to this as if it's odd.
EDIT: I discovered that Cougfan.com wrote a story about it back in 2001. Here's an excerpt for you, as told by the fan: Terry Smith.
Said Smith, "They had (Jim) Plunkett at quarterback, of course, but they didn't have to throw it much. They just kept running it around the left side, coming our way all the time and nobody could stop him 'em. They got it down to about the 25-yard line and I kept telling my friends, "If they keep making that left run, I'll go out there and tackle him."
After a little nudging from his friends, he finally went over the ledge. The newspaper account had Smith telling a buddy, "This is no good," before heading over the railing when Plunkett handed off to sophomore Eric Cross.
"Everybody was yelling at me," Smith told Blanchette. "I actually had this moment of clarity - how stupid this was and how I'd better not do it. But all of a sudden, he was at the 5-yard line and I was out there.'"
Cross was darting toward the end zone. He checked over his right shoulder when a blur appeared in his peripheral vision on the left.
"I swear he could have gone around me," Smith said, "but he lowered his head with his helmet and everything. I remember thinking, Oh, God. I had a football coach at Richland High School, Fran Rish, who used to tell me, `Terry, get your big ass down.' So I hit him as low as I could -- and he went flying one way, and I went flying the other.''