Kelley and Whitney weren't in the opening credits but both actually were on contract if I remember correctly, they weren't day players. And even if they were they were both intended to play larger roles than the others, that's obvious looking at the early episodes, they are both heavily featured.
Takei was always mediocre, forget TOS for a moment, look at his appearance on Voyager, he wasn't good and it was obvious he could never carry a show.
Takei was always mediocre, forget TOS for a moment, look at his appearance on Voyager, he wasn't good and it was obvious he could never carry a show.