When you watch the news and see someone getting arrested... you say "It's off to the cidhna mine with you!" as you then watch your friends and family look at you with a puzzled face.
When you start to change your vocabulary. Instead of using hell you replace it with oblivion and when someone does something nice to you... you reply back with "The divines smiles on you, friend"
When you go on the internet forum sites (Like this one) and you start taking skyrims politics very seriously. If you're an imperial supporter you will say nothing but bad things about the stormcloaks no matter what, and vice versa.
You walk outside where nobody can see you. After you're alone you try to use your mind to release magic flames from of your hand (Hey is worth a shot).
When you spend too much time playing Skyrim and not enough RL time.
When you're out in public and see a security guard you have this strong urge to walk in front of him and ask him if he took an arrow to the knee. Same with law enforcement officers.