The only way to become a mutant is via a mutation, but a mutation does not guarantee a unique phenotype. (I'm assuming, here, that you're using a biological definition of "mutant" and not a more fanciful definition.)
A mutant.
Animals become mutant because of several reasons. One of which is pollution. Poisonous substances caused by pollution can alter the metabolism of animals which can lead Mutation. Like Teenage Mutant Ninja Turtles, we can see that there is some poisonous goo that turned them into freaks.
A mutant can be mutated just as any other life form.
Everyone is a mutation to a greater or lesser degree, just look around you and you will see a mutant.
Blue eyes were caused by a genetic mutation.
A mutagen is a substance that CAUSES a mutation. Essentially, mutagens are the cause, mutations are the effect. Simple as that :)
Humans can find toxic waste. Then you pour it on yourself. Hoping you don't die or kill anyone. SO that's how you turn into a mutant.
Teenage Mutant Ninja Turtles - 2012 The Mutation Situation 2-1 was released on: USA: 12 October 2013 Netherlands: 9 March 2014
You cannot.
Not with natural reproduction. If you cloned the parent that had the somatic mutation, you could pass it on to the offspring if you used the nucleus from the cell that had the somatic mutation.
Monkeys had a strange mutant child who was smarter than anyone else. The mutant child then had more mutant children who were the first humans.
During the 1997 series, Ninja Turtles: Next Mutation