Litt Up (or You Just Got Litt Up) is catchphrase invented and used by Louis Litt. In episode "Bad Faith" he got it registered as a trademark and also received mugs with printing You Just Got Litt Up. In bonus video of Suits Recruits it is seen that coming up with a catchphrase was one of Louis' goals.
The "Litt Up" mugs and T-shirts are also official souvenirs of Suits TV series.
↑Bad Faith (September 10, 2013). Season 3, Episode 9.