The Planets

The Aliens arrive from 10 different (unique) planets: Aquaria, Crimson City, Heaven's Gate, Hydropia, Lavenderia, Magentia, Mineral District, Petraville, Serenity and Snotropolis.

Each planet has 51 Aliens native to it, hence the name, "51 Aliens".

Here are links to all 10 planets:

pageAquaria

pageCrimson City

pageHeaven's Gate

pageHydropia

pageLavenderia

pageMagentia

pageMineral District

pagePetraville

pageSerenity

pageSnotropolis