Twinbrook is a town which shipped with The Sims 3: Ambitions. It is most likely named after the twin rivers that flow on either side of the richer part of the town, near households such as the Whelohffs.
Grant Rodiek first mentioned Twinbrook in an interview, saying;
"The town of Twinbrook is absolutely beautiful and designed specifically for players. You will clearly see how our world-designing team has improved when you discover Twinbrook."
Twinbrook is situated on a bayou (swamp), with many bridges and may be in the state of Simisouri (according to DeAndre Wolf's bio). Much of the town is designed in a French style like many bayou towns. For example, the town library is a classic French design with two porticos, one at both entrances.
According to a Gamespot hands-on, Twinbrook 'is a fictitious bayou town not unlike a backwoods suburb of Louisiana.'Players who attended the UK hands on event reported that Twinbrook is 'a huge new town, which had been flooded, and is now half-swamp half-town. The swampy areas are very dank and misty. The other side of Twinbrook has brand new shops such as the laundromat, the tattoo parlor and stylist shop and much more. I really enjoyed having a look around Twinbrook, and the place looks really great. They've also re-done most of the rabbit holes, such as the diner.' It may be assumed that Simslaus Creek references Stanislaus County, a county located in California, or the Stanislaus River located in said county.
Interestingly, all the pre-made deceased Sims in Twinbrook are pale green if resurrected. They also have gray hair, are all barefoot, and most (if not all) like the color grey. In this post on thesims3.com, SimGuruLily says that this was intentional, but does not say what the intent was. It is very possible that this is a reference to classic comic book supervillian Solomon Grundy, who was resurrected after being "buried" in a swamp, emerging as a green-skinned, white-haired, bare-footed demi-zombie. Twinbrook from aboveThe town appears to have a larger population of rich Sims than Sunset Valley or Riverview has. These families include theWhelohffs, Pidgins, Knacks, and the Bakers. Additionally, several of the houses belonging to the rich are larger than the Sunset Valleyand Riverview wealthy families; most families in Twinbrook start with §5,000 or §10,000 in cash, while in the other neighborhood almost all families start with around §1000 in cash. Therefore, Twinbrook is, by far, the most wealthy neighborhood in the game after Bridgeport.
Twinbrook is technically an island. This fact is hard to discover, but in gameplay, upon visiting map view and pressing tab, you are able to view a wider range of the town. Unusually, if you follow the river near the Rackets' house, there seem to be buildings which look like skyscrapers. Some people think it is a reference to Bridgeport. The only other worlds which have this are Champs Les Sims and Bridgeport.