Originally Posted by
Grunty
I assume physicaly "mutated", as in recognizable by their external appearance which is by some element altered in a way which doesn't matches regular human spectrum of appearances.
Which is actualy quite an interesting subject when it comes to observing the fandom/viewership of the X-men franchise and their expectation of what defines a mutant.
Because in pop culture the world "mutant" when it comes to being applied to fictional humans usualy evokes the image of people with often super natural physical alteration or deformities. In this context super natural abilities are actualy a side effect of the physical mutation, rather than being the source of the alteration. Like someone who is turned into a lizard being having gained super natural strength and regeneration qualities from being made lizard like.
As a result people who hear a character is a "mutant" will more often than not expect abnormal appearance and when a mutant has a regular human appearance it will come of as unusual or suprising.
This kind of expectation of appearance associated with the term is even observable among the Marvel mutants, when an artist is tasked with showcasing a large group of them and often just draws a lot of people with weird skin colors or animalistic/insectiod physical appearance features.
This also has the advantage (from an artistic perspective) to allow the reader to easily identify mutants when they are used as victims of agression and hate, without actualy having to come up with some unique super natural power or an incident in which they used them.
However as we know, with X-gene mutants the appearance vs. power dynamic is actualy inversed to pop culture. Mutants are defined by having super powers from a wide spectrum of fanastical ideas, from physical understandable powers like kinesis or psychic powers to absurdly fanastical like manipulation of concepts and ideas (see that new character to appear in New Mutants), while physical alterations is in theory merely a possibility as side or direct effect of powers.
So in regards to mutants appearing on screen, in theory hardly any of them actualy need to look unnatural or altered, but it would allow the viewer to be able to quickly identify them as such.