Yep - almost all the original crew doing the voices, many of the top sci fi authors from the original series writing, and a chance to do some wacky aliens cos they didn't have to glue some Hollywood gumby into a latex monster suit.
It comes from that weird decade long period where the entire cast were being paid on pay or play deals while they tried to get the show back on TV or onto the big screen, cos the original show was a monster hit in syndication.