Travolta, Alley reunite in sitcom
The pair appeared together in the 1989 film Look Who's Talking and now John is making a rare TV appearance with his old pal, reported Deadline.
He said: "I'm excited about working with Kirstie again, in addition to such terrific talent on the show. It's always a treat to be surrounded by people you respect so much both personally and professionally."
Kirstie's New Show features Fat Actress star Kirstie as Broadway performer Maddie.
Her son Arlo (Eric Petersen), who she gave up at birth, reappears after his adoptive parents die and tries to build a relationship with the star.
John plays a stagehand who Maddie has a one-night stand with but who refuses to leave her alone.