Complex sentence: While promoting the film in 1989, Douglas and DeVito appeared on Arsenio Hall's late-night talk show, "The Arsenio Hall Show", somewhat aloofly, gave away the ending to the film, much to the apparent shock of his two guests.
Split into simpler sentences: While promoting the film in 1989, Douglas and DeVito appeared on Arsenio Hall's late-night talk show. Hall, somewhat aloofly, gave away the ending to the film, much to the apparent shock of his two guests.