Wikipedia
Goobacks
"Goobacks" is the seventh episode of the eighth season of the animated television series South Park, and the 118th overall episode of the series. It originally aired on Comedy Central in the United States on April 28, 2004. In the episode, people from a poverty-stricken future travel back in time to find work, affecting the town's economy and the employment of the original occupants.
"Goobacks" serves as a satire of illegal immigration, and mocks both sides of the debate concerning it. The episode is widely remembered as the origin of the catchphrase "They took our jobs!".