Portmanteau of "Skill Issue", a phrase often used by gamers and social media users in general to point out someone's shortcomings, no matter the scale of the mistake(s) made. Modern equivalent of Epic Fail, Git Gud etc.
"Dude I can't even beat the first boss of Dark Souls, how do peoplespeedrun this game?"
A person pretending to be something they aren't, or an impostor. This is inferred because of the old alien movies where alien pods appear on earth and the "pod people" dispose of the humans and slowly reproduce the bodies, pretending to be humans.
The pod person was pretending to be my father, but I knew that he was an alien when he acted differently than my father ever would have.