Lego City is a theme under which Lego building sets are released based on city life, with the models depicting city and emergency services (such as police and fire), airport, train, construction, and civilian services. Legoland Town is one of the three original themes that Lego produced upon its launch of the Lego minifigure in 1978 along with Castle and Space. The Town brand was briefly replaced with Lego World City in 2003 and 2004 before it was simply rebranded as Lego City in 2005. The Lego City theme traces its origins to Lego Town, a theme introduced with the first minifigures in 1978, when a completely new range of buildings and vehicles were introduced for the European markets, although Lego sets with city buildings and vehicles had been commonplace since the late 1960s. In 1975, a precursor to the minifigure was introduced, in the same scale but without moving parts. Through the mid-1970s Town sets had buildings and vehicles functioning more as models, with minifigures unable to ride the vehicles. This continued with the new minifigures, for some of the sets in its early years. In 1980, the Trains theme was completely revamped to complement the Town sets. By 1983, the remaining vehicle based sets that were not minifigure compatible had been discontinued. All sets were originally released under the "Legoland" label until it was discontinued and replaced with "Lego System" branding in 1991. Eventually, different subthemes under the "Town" brand were used to tie together related sets, such as police, coast guard, emergency services, airport, road rescue, trains, fire, and harbor. In 1999 Lego Town was replaced by City which was known as Lego City Center in The United States. The theme was discontinued in 2002, and replaced by Lego World City in 2003. During the Christmas season, a City-themed advent calendar set is sold through the online Lego Shop and at retailers. On June 22, 2019, Lego City Adventures aired on Nickelodeon during a Saturday morning lineup along with SpongeBob SquarePants.