Crossed da border, eh, to see Iggy and the Stooges at the Windsor Ice Arena(?) back in '72(?). Iggy was Iggy - clad only in a silver glitter G-string, spitting on the crowd, acting a real wild child - when two members of the band started arguing with one another during a song. As the argument continued it eventually escalated into a knock down, fisticuff, brawl between the two right in mid-song. It was hilarious, the two rolling around on stage battling while the rest of the band tried to keep the song going. We decided it was time to leave then. Still had a great time though.
Same era different show, though this one only a near awry, Johnny Winter at Cobo Hall. The crowd got so rowdy (fights, flying beer bottles) they turned the house lights on, interrupting the show. A Cobo usher/manager got on stage and took over Johnnys mic. He threatened to end the show if we all didnt settle down. Johnny told him to get the f*** off the stage, regained possession of the mic stand and went into a blisteringly rocking song. The crowd turned even nuttier, of course. Depending on your perspective: Cobo Hall operators likely felt the show went awry; the audience had a great time, though it could have easily gone awry for us as well.