By SOPHFRONIA SCOTT GREGORY

Calling all Trekkies! Mark your calendars! Set those vcrs! This year's cliffhanger of Star Trek: The Next Generation is one to go warp over. Famed physicist, best-selling author and all-around science god STEPHEN HAWKING makes a cameo appearance as a holographic image of himself matching wits at a poker table with the android Data and Albert Einstein. Hawking, who suffers from Lou Gehrig's disease and communicates by computer, is a big-time Trekkie and got invited to do the star turn, which airs the week of June 21, during a visit to the show's studios.