List of Some LOST Alumni Guest Appearances on H50
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http://www.imdb.com/title/tt1600194/board/nest/241976609?d=241982322#241982322
[Edit / Update]
Sorry, the post linked above
has expired off that board.
Here's a list of H50+Lost cast & crew:
www.imdb.com/search/name?roles=tt0411008,tt1600194