What's On Today.

10 P.M. (USA) PSYCH Shawn (James Roday) and Gus (Dule Hill) help a girl free a mall Santa from jail, only to discover that they've been conned. They have assistance from Gus's visiting sister, Joy (Faune Chambers), who is intent on repeating a fling she had with Shawn. Keith David and Phylicia Rashad guest star as Gus's parents; John Landis directed this hourlong holiday episode. (Above, Mr. Roday, right, and Mr. Hill flank Santa.) 8 A.M. (Sci Fi) MORK & MINDY Nanu-nanu! Sci Fi devotes 22 hours of programming to the 1978 ''Happy Days'' spinoff that rocketed Robin Williams to fame as a zany alien from the planet Ork, who receives help acclimating to Earth from a sweet-natured human (Pam Dawber) in Boulder, Colo. [ABSTRACT FROM PUBLISHER]