The Day The Earth Stood Still SPOILER ALERT:
You never know how much a studio will use and re-use its own material for future productions. The following 20th Century Fox Studios projects make a great example. In the first season of Lost In Space, Michael Rennie played a Klaatu-like character called the Keeper in which he collected alien species for further study on his home planet.
Ironically, the primary focus of Klaatu in the 2008 incarnation was to preserve as many of the Earth species as possible species of Earth much the way his character had done in The Keeper episodes. Klaatu was here to take away all the species except for us naughty humans.
Side note: Okay here's the sci-fi geek in me. 20th Century Fox also used stock music from the original The Day The Earth Stood Still in many Michael Rennie scenes, which they also did for several of the Irwin Allen series including Voyage to the Bottom of the Sea all the way through The Time Tunnel where ever a 'sci-fi ambience' was needed.