The opening of “Quidam,’’ the Cirque du Soleil production currently playing at the Agganis Arena, feels like it was lifted right out of “The Cat in the Hat.’’ A bored little girl named Zoe (Alessandra Gonzalez), stuck at home and ignored by her parents on a rainy day, finds a hat left behind by a mysterious visitor. She dons the hat and is led on an adventure, not by “The Cat in the Hat,’’ but by a quirky ringmaster named John (Mark Ward), whose look and attitude is reminiscent of Pee-wee Herman. Although Zoe reappears consistently throughout the piece, for “Quidam,’’ the theme of a lonely girl’s imaginary dreams is less important than Cirque du Soleil’s extraordinary mix of jaw-dropping circus acts and old-fashioned comic clown routines, held together by an eclectic and dramatic musical score, played by a stellar six-piece band.