Nothing gets a pop song stuck in your head like dancing with a flash mob to it. Flash dancers around the country are probably still hearing echoes of Katy Perry's "Firework" after participating in a Fourth of July flash dance. Luckily, Perry has more than enough No. 1 hits to keep you rocking at this cost-efficient show (highest-priced regular admission ticket is $45). At that price, you can stand one more rendition of "Firework." Perry's California Dreams tour bumps up against the Britney Spears tour at the United Center (both shows are Friday). But, if Perry's No. 1 spot on MTV's Summer Jam poll is any indication of what's hot in pop, she will deliver a show-stopping performance even without a dynamo backup like Nicki Minaj on her bill.
7:30 p.m. Friday at Allstate Arena, 6920 N. Mannheim Road, Rosemont; $25-$45; 800-745-3000, ticketmaster.com