Polka has taken over. Just turn on the radio. Open a magazine. It's everywhere. The worldwide polka explosion is about to reach critical mass, and the good people of Ennis, Texas are firmly planted in its nexus, ready to withstand the massive aftershocks. I'm not sure if that last sentence is scientifically accurate, but I do know this: The 40th Annual National Polka Festivalis under way in Ennis this Memorial Day weekend. This is polka's Woodstock, Lollapalooza and Ozzfest all rolled into one, only with better food and slightly less expensive beverages. There'll be polka parades, polka dancing, over a dozen polka bands and three air-conditioned fraternal halls ready to get their roofs rocked off. Where else are you going to simultaneously do the chicken dance with Polka Dot the Chicken while shaking your tail feather with the Bud Girls? Those Bud Girls are pretty discriminating. They don't appear at just any outdoor festival. And it wouldn't be a polka party around here without Brave Combo kickin' out the jams. The many accordions of the National Polka Festival will shred this weekend throughout the great city of Ennis. Admission to events is $6 on Friday, $10 on Saturday and $8 on Sunday. For more info visit nationalpolkafestival.com.