You can apply physics to the size of people.

The structural support necessary for a giant is an interesting question.

I read somewhere that the thickness of the bones necessary to support a "giant" body becomes a limiting factor.

Also if you come from a giant planet, they you have to contend with the higher gravity associated with a larger planet.

I think that the aliens would look significantly different than us.

of course it is possible...anything imaginable is possible.....expand your minds and see the truth.....i can picture an alien holding our planet in his hands...why not ?

dinosaurs and stuff were really big because the enviroment had a lot more oxygen, so if they could get big on ours they could probly still get big on theirs. creatures on this earth in the past have gotten huge though.

The Universe is a very large place. Anything is possible.