The Rascals — the 1960s band fond of dropping their G’s in hits like “Good Lovin’ ” and “Groovin’ ” — reunited to play their first public show in 40 years last week. The evening marked the opening of “Once Upon a Dream,” a new “theatrical concert” produced by E Street Band guitarist Steven Van Zandt. The six-night run at the Capitol Theatre in Port Chester includes original members Felix Cavaliere, Eddie Brigati, Gene Cornish and Dino Danelli as well as screened archival footage and interviews. Chazz Palminteri, “The Sopranos” star Vincent Pastore and record mogul Tommy Mottola were spotted rockin’ out.