Photoshop
You have to be lucky enough to have an alien capsule crash land near you and you have to be the first one to find it. Not only that, but it also must contain the universe's only Omnitrix. You are more likely to be struck by lightening 728 times (given that you survive each consecutive time). Otherwise, you have to have a knowledge of science and mathematics that is far beyond our comprehension in order to make your own Omnitrix which will be nothing but a pretty and high-tech watch because you haven't explored enough universe to collect the DNA of the alien(s) you wish to turn into and even then there are likely to be problems and/or complications as yours is nothing but a cheap imitation.
Another option is to aim for a career in acting. Two young actors have successfully transformed into aliens for the Cartoon Network big screen. You could be next. (Even then, it's really
Photoshop and really expensive special effects that do this, so there is currently no way you can turn into a Ben 10 Alien.)
