There are certain sure things when you see Iggy Pop perform, with the Stooges or Stoogeless. He will dump copious amounts of water on his head; hump a speaker (or two, perhaps more than once); roll on the stage; invite dozens of kids up to sing along to a Stooges song; and, invariably, lose his pants and expose some part of his six-decades-old private bits.

Shockingly, for the first time in all the many times I’ve seen Iggy, his impossibly low-rise jeans stayed put during the Stooges’ entire set. I can’t say I was disappointed, but I was a bit scared for the man who has cheated death more times than Velvet Revolver and all of Mötley Crüe. After barreling through death-rattle punk-blues takes on “1969,” “I Wanna Be Your Dog” and “TV Eye,” Pop, who introduced the band as the “f—ing Stooges” and said he was glad to be at Lollapapalooza, invited the kids up for “No Fun.”

They jumped the barriers up front and filled the stage. And then, like sweaty, sunstroked (or is it sunstoked?) rats fleeing a chest-crushing pit, they kept coming — and coming and coming and coming. What was a fun sing-along with a few hundred of Iggy’s friends quickly turned into what Pop would later refer to as a “catastraf—.” With the singing and the grab-ass done, Pop thanked his friends, but they wouldn’t budge. If it seemed like security had lost control before, now it definitely felt like someone was gonna go home on their back.

Pop, who is normally impossible to phase, no matter what the chaos, began to seem genuinely freaked out by the wall of fist-pumping “Yeah, man! Iggy!” screaming masses. “Now we have to calm down,” Pop said, sounding, perhaps for the first time, like the 60-year-old that he is, continued to plead. “Easy baby … all right, we gotta cool it down. It was fun, but it can’t go any farther.”

At last, unable to tame the horde, Pop resorted to hiding behind bassist Mike Watt’s amp as the video feed to the screen on the side of the stage cut out and was replaced by a generic crowd-information message that read, “Lost Anything?” Yeah, Ig, like maybe control of your stage? The music sounded dangerous and raw, but the threat of a stage collapse felt even more perilous.

Read more about Iggy Pop and all of Sunday’s performances on MTVNews.com …