For large ensemble TV show casts, the typical promo photo tend to be a wide shot with everyone standing, with minimal body overlap. It seems like you would need a wide angle to get the whole scene if they are shooting in a studio, but the verticals are perfect at the edges.
How would you replicate this? And is it possible these are photoshopped together from separate portraits?
Examples (you can find many more by image searching for "cast photo"):
These are Photoshopped. Each actor is photographed separately or in small groups as appropriate. Then each actor is cut out of their original image and placed in an empty background (either photographed or computer generated).
You can see in some cases that the angle at which the subjects' feet meet the ground isn't quite right (take a look at Christina Hendricks' feet, the red-head in the Mad Men shot, and Kiefer Sutherland's feet in the 24 shot), and that there is no interaction between any of the subjects (apart from where they've been photographed together, as in the guy sat down on the right of the Mad Men shot, where you can see the woman's skirt being pushed in by the chair).
Overall it's pretty simple stuff. The trickiest bit is making sure the lighting of the subjects is consistent (both between subjects and with the background: the 24 shot is a bit dodgy in this regard, it looks like the Kiefer Sutherland shot is from a completely different shoot); the Photoshopping is elementary stuff.
On the first case is pretty obvious that they are at least 5 images. (4+1 background)
You have a lateral and backlight where each consecutive group would cast a shadow on the group in front.
But some magazines are famous of actually taking a large group.
Take a look at this search https://www.google.com.mx/search?q=vanity+fair+large+group+photoshoot&dcr=0&tbm=isch&source=lnt&tbs=isz:lt,islt:2mp&sa=X&ved=0ahUKEwiH5faRrtHZAhVNylMKHZQ7B0sQpwUIHw&biw=1366&bih=700&dpr=1#imgrc=9KzusaYtQPz9zM:
(This is actually not one photo either but a composite shot to add the photographer and asistant into the photo), but you will notice that in a real group photoshoot they are using a "butterfly" light scheme. This is using a large softbox above the camera so each member do not cast a shadow on the next one. If they also use one below would be a clamp light scheme.
The lighting is the most complex subject here.
In regards to using a wide lens, no. If you want a quality photo you would not use one, but use a really large studio so you can go back far enough.
You also would not use a small sensor camera, but a medium format, so the focal length is not really small.
How do they shoot wide television-show cast photos?
One actor at a time. Then they composite them together. That's pretty much it.
