sentences:  Because of this, he was the only one not to receive his invitation to Sheridan's farewell party in "Sleeping in Light", though Allan would still meet Sheridan one more time as Sheridan took one last walk through the station.In "Sleeping in Light", he walked with a noticeable limp, which has never been explained on screen.In the voiceover commentary of the episode, series creator J. Michael Straczynski explained that Zack was involved in heroic activity and lost his leg.