. [5] http://www.dailymotion.com/embed/video/x437pz Celebrity Rehab: Jeff Conaway by TheDlisted Grease and Taxi The following year, Conaway appeared in the original cast of the Broadway musical Grease , as an understudy to several roles including that of the lead male character, Danny Zuko, and eventually succeeded role-originator Barry Bostwick . [4] [9]