I just downloaded the latest issue of The Sims Magazine and there's one article that's really interesting. I'm talking about the Simlish article. It's pretty cool. I've always found Simlish fascinating and I know I'm not the only one. 
Here's a snippet from the article:
Developed collaboratively by Will Wright and his audio team, Simlish made its quiet debut in SimCopter — albeit in a very scaled-back form — but it wasn’t until the arrival of The Sims that it really took on a life of its own. The original plan drew from actual languages, including Ukrainian, Latin, French, Finish and Tagalog, though the end result took a different direction.
“They ultimately decided that Simlish worked best as a ‘language’ made up of gibberish words that couldn’t be translated, so that its meaning would be left open to the imagination of the player,” said Bill Cameron, voice director for The Sims. “The actual sound of Simlish was created by two wonderfully talented voice actors named Stephen Kearin and Gerri Lawlor... brilliant improvisers who worked with Maxis to bring the language to life.”
Technically, Simlish is a substitute for language rather than an actual one, Cameron points out. Not many of the common phrases you hear in the game have a one-to-one match in English or any other language, though some have taken on meanings in the game.
