I have a theory as to the reason Lotor became a part of the series. I tend to think that, originally, when the series was being made, the creators didn't really plan on having him involved. With the exception of Nanny, all the main characters are there from the onset of the series. Oh, various one-shot characters appeared, but for the most part, the cast remains the same. Sven disappeared for a while, but he was there at the beginning. Anyhow, in an early episode, before Lotor came about, Zarkon and his witch, Haggar, created a robeast in the shape of a handsome, white-haired prince. He was suave, this prince, and started to win the heart of Allura (as I remember it...I'd best go back and search through my tapes to see if this was so. It's been a while.). He was a snappy dresser (Tights! Wow!) and he seemed to hold a fondness for her. Well...he was, of course, discovered to be a robeast and subsequently defeated. Now, I tend to think that during the time that Voltron was being aired as Golion in Japan, this false-prince probably was rather popular. Obviously, he died at the end, so there was no way to bring him back without delving into the over-done "he got better" thing. Thus, there was no wayward prince to taunt Allura with his fondness for her. What to do? Bring in the son of Zarkon! Here would be a handsome, white-haired prince with a fondness for her....deja vu, eh? Now, I could be VERY off with this, of course, but even back when I was but a small child, I thought the reasons I just presented were the cause. In any case, Lotor appeared and brightened up the show, in my humble opinion.
Humble opinion time (TM). I really don't feel that some of the episodes involving Merla and Lotor were in keeping with his original personality. Now, I know on the main page I mentioned that I didn't think Lotor was in the original plan, and now I mention Merla, yet another new character. Well, the thing is, the second season of Voltron was created for the American audiences. The first season was created by a Japanese company, then dubbed and shipped to America. Not so with the second season...in fact, that one was created (supposedly) here in the States. (Mind you, this is 3rd hand information, soooo...) Anyhow, in one episode, Lotor pretends to have fallen for Merla, traps the Voltron force by tricking her, and locks them in a bubble to be killed. He didn't even think twice about locking Allura up, although he did grab her hand and propose - yet again. However, he didn't appear to really give a damn about her imminent death. Now, that doesn't sit well with me. Here we have a man who is convinced that Allura is the only one in the entire Universe who could ever possibly be his bride. Why, then, would he be so casual about her dying a horrible death along with her comrades? I maintain that he would not. Even if he were tired of persuing her, I sincerely doubt he'd become so callous towards her welfare as he appeared to have turned.