Complex sentence: The production of the episode reunited fellow' alumni Burton as the director, who previously played Geordi La Forge, with alumni Brent Spiner as Arik Soong, who previously played Data.
Split into simpler sentences: The production of the episode reunited fellow' alumni Burton and Brent Spiner. Burton, who directed the episode, previously played Geordi La Forge, while Spiner, who played Arik Soong, previously played Data.