There are three major series continuities: Tenchi Muyo! Ryo-Ohki (Tenchi Muyo!), Tenchi TV (Tenchi Universe), and Shin Tenchi TV (Tenchi in Tokyo). The first series, Tenchi Muyo! Ryo-Ohki, is the original OVA which introduces the core characters. Tenchi TV and Shin Tenchi TV are alternate stories that utilize the same characters, with the addition of Kiyone Makibi. The first of the spin-offs was Tenchi Muyo! TV, in 1995 (known to American audiences as Tenchi Universe); it is a twenty-six episode TV series that retells the original story, documenting how everyone met and changing the back story of some characters. Shin Tenchi TV, aka Tenchi in Tokyo is considered another retelling, chronicling Tenchi Masaki's move to Tokyo. Some character personalities are also changed in this incarnation as well.<br/><br/>^It's from Wikipedia so you know it's true.^