This is 'hello' in Simlish. Simlish is the language that Sims speak. Whilst playing The Sims 2 or The Sims 3, when Sims greet each other they say 'sul sul'.
A form of saying "what's up?," derived from the poor grammatical abilities of a man in Bradford, PA. Wal Sul has been manipulated over time and still can be, due to a liberal vernacular. It's main region of use is NW Pennsylvania.