It would be difficult to imagine the show without Dr. Smith and the robot, but that's how it was in the original pilot (the most expensive to date) that the PTB at CBS watched. There were many differences. First the Jupiter 2 was named, I think, the Gemini XII and had only one deck. After blast-off, it was caught in a meteor storm that severely damaged the ship and sent it wildly off course for three years with the family and "Dr." West remaining in suspended animation until it was caught in the gravitational pull of a planet and crashed. Fortunately, it was hospitable to human life and the "freezing tubes" opened. Months later, the Robinsons had set up camp including gardens and domesticating several of the world's animals. The Dr.'s Robinson and West discover a massive, deadly cold wave is approaching but before heading back to camp are attacked by the monstrous cyclops. Will rescues them and - after Penny is found after getting lost - head south. They take refuge in the cave city that collapses during a quake and then start sailing through the Inland Sea where they barely survive a vicious storm. When they arrive at the opposite coast, it is a lush, warm tropical region. As they kneel to pray, the don't realize that two aliens are watching them. End of pilot.
The CBS execs liked it, bought it, but insisted that some turmoil must be interjected to "flesh" out the characters. Enter the murderous Colonel Zachery Smith who was to be killed off after a few episodes, and the robot. New scenes were shot and spliced into the pilot stretching it into five episodes.
The unaired pilot (although it did eventually air on Sci-Fi a few times and was also on the previously free Hulu, along with being included in the DVD's) was a bit of a different creature than the Smith/robot version, but it was highly dramatic and exciting, quite serious in the story-telling. Without Smith and the Bumbling Bubblehead, it probably would've remained a straight-forward action drama, more in the vein of Star Trek, rather than becoming the fun, goof-ball attempt to counteract its main time-slot nemesis, Batman.
Gerard