If you’re planning to take the kids out shopping for Halloween gear this weekend, don’t wait too long: Costumes from Star Wars, Minions and Inside Out are already flying off the shelves at local Halloween stores, as are the Avengers and other classic superheroes. Also hot this year is the new breed of inflatable costumes, which come with a battery-powered air pump to keep everything puffy through a long night of trick-or-treating. Popular inflatables include sumo wrestlers, Baymax the robot from Big Hero 6, and the Stay Puft Marshmallow Man from Ghostbusters. But pretty much anything inflatable is a hit at the pop-up store X-treme Halloween on Rockville Pike, says manager Dennis Bracey. “We’ve got a T. Rex, SpongeBob and Patrick the Starfish, and we can’t even keep them in stock.” For the girls, characters from the Monster High franchise and Disney Channel’s Descendants are popular choices this year. But Princess Elsa from Frozen is still holding onto her crown: Just like last year, she remains the top pick for girls who want to be royal.