The "Lost In Space" pilot didn't even have the character. Then, when he was added, he was supposed to be killed off after six episodes.
Guy Williams, June Lockhart and Mark Goddard (although they liked him personally) were not happy with the permanent addition of Jonathan Harris to the show.
I think that’s because they preferred the show be more serious as the early B/W episodes were. The reason it turned “campy” and “cartoonish” was to compete with Batman.
It's always interesting to find out what went on behind the scenes, and also to see the changes that take place as they find out what clicks with an audience. The other reason they were probably not happy is that the show as conceived featured them as the stars, and they ended up being background noise.
This happens a lot behind the scenes. IIRC, in Family Ties, Alex Keaton was supposed to be a background character and the show was supposed to focus on Meredith Baxter-Birney. She didn't complain loudly, but was a little frustrated that she ended up being a supporting character in what was supposed to be her "star vehicle."
Fonzie wasn't supposed to dominate Happy Days. Urkel was intended as a background character in Family Matters. Supposedly, Shelly Long wanted Frasier written out of Cheers, as she wanted the focus of the show to be on the relationship between Diane and Sam. Frasier was originally intended to be a short term character, only there for the episodes when he was going with Diane. Another bit of trivia on Cheers is that supposedly the cast relationship with Long was similar to the plot relationship with Diane; she was the oddball outcast and perceived as a Diva. Saw the 200th anniversary rerun that had all the cast members. When they talked about "Coach," who had passed away, she said something like, "He was my, he was Diane's only friend at the bar." I don't remember the exact wording, but the way she phrased it you couldn't tell if she was referring to character relationships in the show or cast relationships behind the scenes.