I've always wondered about Chapel's involvement in TMP. It seems strange, as she's basically bumped up to doctor but doesn't really do anything more than she already did in TOS (of course, Phase II might have intended to use the character more thoroughly -- TMP was
only the pilot episode after all).
The same with Rand. It's nice to see the lovely Grace Lee, but she's kinda a cameo isn't she? So is Chapel. It's a bit like TMP is trying to appeal to the fanbase, maybe a bit like those television reunion show specials. You know the sort of thing: "Hey look folks, the whole gang's back together again! Even Janice Rand is here!".