If we told you an artist played a new track called “Dad Vibes” at something called the “Bud Light Seltzer stage,” you’d automatically assume we were talking about Jimmy Buffett. But no, it was Limp Bizkit, serving the most unnerving reflection on aging since M. Night Shyamalan asked What if there was a beach that made you old? At Lollapalooza in Chicago’s Grant Park on Saturday, the throwback rap-rock group began their set with Wes Borland in a mask covering everything but his mouth, just wailing away on guitar. It was the lead-up to Fred Durst debuting his new look, in a puffy jacket, tinted shades, and gray handlebar ’stache. They ended the set with the aforementioned track, which begins (oy vey), “Check out the dad with the swag on the flow.” Notorious P.I.G. energy.