Origin
“Shit just got real” originated from the 2003 movie Bad Boys 2. Long story short, one of the main characters gets a phone call. He suddenly notices how much danger his friend and he are in, to which he responds “Shit just got real.” It was also referenced in the 2007 film Hot Fuzz.
Note: Yes, I know the Hot Fuzz clip isn’t just the clip. It was the best one I could find at the moment and I’m gonna’ try and find a better one later.
Use
When people use this, it’s usually to denote how a situation gets suddenly dangerous/hostile. Let’s say person A is joking with person B. Person B turns it into an insult and things start to escalate. Right there would be a perfect time to say “Shit just got real.” What was just a minute or two ago a friendly conversation is almost an all out fight.
Another example would be somebody just noticing how dangerous a situation is getting. Person A and person B are friends again. They decide it would be awesome to build a bomb. When they set it off, it leaves a two foot deep crater in the ground and sprays fragments and debris all over. That would be a perfect moment to say “Shit just got real.” What at first seemed like an awesome idea or situation turns out to be extremely dangerous.
Spread
After the movie was out for while, an Urban Dictionary definition was created. Despite this, Googling “Shit Just Got Real” didn’t yield any relevant results until Jan. 2004. By March, usage grew a little, with the first five results being relevant. By September 2004, there was enough relevant results to fill a page. By June of ’07, a YTMND and Facebook page were made for the phrase.
Sorry, there’s wasn’t enough searches for it to get decent results on Google Trends.