The nun looked angry. Fighting mad. It’s funny, the snapshots that stick.

One was of that welcoming bedsheet hanging from a dormitory window on the Notre Dame campus that Saturday in 1988. Spray-painted in black, it read “Catholics vs. Convicts” and bore a rough likeness of Miami coach Jimmy Johnson with devil’s horns. T-shirts all over South Bend, Ind., dubbed the cherubic Johnson “Pork-Faced Satan.”

But the image that sticks most is of the look on the face of that one nun in the smoke-gray habit as the Hurricanes ran onto the field before the game that day. Her features screwed tight as if she had bitten into a lemon. She pointed a rigid index finger at the field. What she yelled was a pantomime to me through the press-box glass.

I covered UM football full-time those years when I coined the Canes as “The Best and Baddest Team in America” for its dominance on the field and controversies off it. That was back when The U really did invent swagger. Back when the Notre Dame rivalry reached a full boil, bookended by those games in 1985 and ’88.

Not in most of a lifetime chronicling sports have I see anything quite like it.

Maybe it was the audible crunch of UM safety Bennie Blades tackling Irish receiver Tim Brown so hard Brown said afterward he worried the Canes would follow him into the parking lot and beat him up. Blades had stood lording over the prone Brown like a prizefighter hearing the count.

Or maybe it was the recollection of Miami’s team priest ducking the flying trashcan on the sideline in South Bend.

Miami-Notre Dame owned the national stage as a rivalry a quarter century ago yet the nostalgia roars back like it never left as the teams prepare to play again Saturday night in Chicago. But it isn’t romanticized nostalgia with soft edges. It is visceral.

In 1985 the Canes swamped Notre Dame 58-7 in Miami, Johnson showing no mercy in the final game for coach Gerry Faust.

The Irish would get their revenge in ’88 in a 31-30 win in South Bend that was voted the greatest victory in Notre Dame history. Coach Lou Holtz at halftime had exhorted his Irish to win the fight, then said, “But save Jimmy Johnson’s ass for me!” as his locker room erupted in cheers.

Into a third decade later those games remain like a cottage industry for Holtz and Johnson, both retired now into TV commentary.

This week Holtz delighted to recycle one of his classic lines: “That whole ‘Catholics vs. Convicts’ thing was not fair,” he said Tuesday, with a comedian’s timing. “It was not accurate, because a lot of our players were not Catholic.”

Johnson, for his part, laughs off that halftime speech by “scrawny Lou Holtz.”

Yes, it’s fun to relive the highest days of a rivalry that seemed anything but fun at the time, but here’s the thing.

“Then” doesn’t matter as much as it might have, because “now” is relevant again, finally, for these two programs.

Nostalgia is great if it’s all you have, but Miami and Notre Dame have more now, and proving that is a lot of what Saturday night at Soldier Field will be about.

It is the school’s first regular-season meeting since 1990 (with two more games scheduled in 2016-17). They met in the 2010 Sun Bowl, an easy Notre Dame win, but that was forgettable other than it being the first time Al Golden watched his Canes as new coach, from a suite in an observer’s role just days after replacing fired Randy Shannon.