Speaking from experience, if an artist is instructed to do likenesses he's severely limited by the number and quality of stills the client provides. Few artists, even the best ones, can fake a convincing likeness at an angle for which they don't have reference--for instance you need a profile but all your stills are three-quarter shots. Some clients allow the artist to draw a "sorta-like" character who looks enough like the actor to get the nod. Alex Toth, Dan Spiegle, and Mike Sekowsky often did that in Dell and Gold Key movie/TV comics. On the other hand if the client is a stickler for likenesses and bounces anything that doesn't look exactly like the actor, then you pop those stills in the old Art-O-Graph and trace them over and over. In this issue look how many times the McHale head in page 4, panel 5 reappears. Or the "Binghampton strokes his chin" shot.
Of course the same thing happens if the artist knows he isn't too hot at likenesses and wants to play it safe. I don't know why, but the ability to capture a likeness freehand and the ability to draw good figures don't necessarily come together. Neal Adamses are few and far between. You'll see superb comic artists who can't do good likenesses and you'll see excellent likeness-getters, portrait artists, for example, who don't draw all that well. There aren't that many movie or TV comics these days, but I speculate that it would be easier to draw one than it was in the McHale's Navy days. You can grab hundreds of frames and get character reference from every angle the director saw fit to photograph.
