An unusual theme appears on the New York stage this fall as two musicals, each in its own way, tackles the subjects of fatherhood and deception. Big Fish, a new musical based on the novel by Daniel Wallace and subsequent film, is a splashy hodgepodge of forgettable music by Andrew Lippa set against the backdrop of a fantastical world created by scenic designer Julian Crouch and costume designer William Ivey Long (with some blurry projections by 59 Productions). The story brings to life the bigger-than-life tales of Edward Bloom as recounted to his son. Downtown, you can catch Lies My Father Told Me (based on the works of Ted Allan and film by the same name), a memory play with music that follows the musings of lead character David as he recalls his tender relationship with his grandfather and the volatile verbal abuses of his father. Neither show manages to find its emotional core, despite moments of honest theatricality that occasionally bubble to the surface.