Spencer Milligan (Park Ranger Rick Marshall) left the television show after the first two seasons over a salary dispute with creators Sid Krofft and Marty Krofft. In an interview for the 2009 movie, Milligan said "We had a difference of opinion, let's put it this way, on using my face for stuff and paying me - lunch boxes, compasses - where they were selling them and I thought it was only fair that everyone should get their fair share." To handle his departure, the storyline was that his character, Rick Marshall disappeared, having may or may not have returned home, and at the same time, his brother, Uncle Jack (Ron Harper), while searching for the trio, stumbled into the "Land of the Lost" and was reunited with his niece and nephew.
There were only 3 Sleestak costumes for use, which required the production team to merge shots and use editing tricks to make it appear that there were more. However nearly all of the time, you will see only 3 on screen.
The producers came up with a very interesting idea to keep their viewers looking at the show during the hiatus between the first and second seasons. In the first season's final episode, the Marshalls discover that for some reason they aren't supposed to be there. Enik later informs them that due to a time disturbance that they never really arrived in the Land of the Lost and must go back in time and relive the accident that brought them there. By going back in time, they also would experience everything that happened to them up to that point in a sort of time loop.
During the final season, the Marshalls and Chaka moved from their cave to a Sleestak temple. A popular myth for the reason of this set-change is tied into the fire that destroyed the cave sets for another Krofft show Sigmund and the Sea Monsters. However, this fire took place during the second season of Sigmund, at which time Land of the Lost would have been in production of only its first season. The first two seasons of Land of the Lost were taped at a different studio (General Service Studios in Hollywood) entirely from that of Sigmund. The show then moved to Goldwyn Studios for its third season. This was the studio where the fire did occur two years prior that destroyed the Sigmund sets.
During the final season two new monsters were introduced, a two-headed monster named Lulu and a fire-breathing monster named Torchy. Lulu was based on the Pleisiosaur, an aquatic reptile from the Cretaceous period, while Torchy was based on the Dimetrodon, a reptile that died out before Earth's Paleozoic Era transformed into the Mesozoic Era.