Wahlberg is in the familiar rapid-fire, rat-a-tat style he has developed over the years, tussling and bantering with everyone around him, and not even his encroaching disability can slow his motor-mouth.

Eldritch’s three stigmata include artificial eyes, a metallic hand, and steel teeth that, for literary scholar Marcus Boon anyway, suggest the motor-mouth jaws of speed freaks.

She delivers stretches of her story in a voice-over that suggests that Mr. Sorkin wrote and directed his movie with a stopwatch in one hand and a DVD of Howard Hawks’s motor-mouth comedy “His Girl Friday” in the other.

As Genie, Murphy goes all out as the showboating, plus-size imp whose motor-mouth riffs are variations on Robin Williams’ hyperactive voicing of Genie on film.

Instead watch him on the practice courts, where you can see up close the full manifestation of his otherworldly talent, but also the internal forces that work constantly at cancelling it out; the darting eyes, the motor-mouth, the kiddish fragility and the inattentiveness.