system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel] What gave away that Forge was a mutant?

Instead of just a really amazing engineer. What did he do that made people think he was genetically different, rather than just great at building stuff?
gpt
He can't explain how his inventions work.  They do, and he has to have a goal when trying to put them together (e.g. make a gun that launches squirrels), but when he gets the squirrel-o-tron working, he can't explain where the squirrels come from, nor how the "grey/red" selector works.  It just does. 

Also, isn't he from the Days of Future Past timeline?  When all there were left were mutants?