The ad was filmed in both London and Prague, where the team took over a shopping mall near the city centre.
Monty Verdi, CHI creative director, said: "We looked at a few, different options. It could have been a cartoon, it could have been CGI. We thought puppets gave us the most charming way of bringing the ideas to life."
The puppets were created by Asylum, the models and effects company that has also worked with Audi, Pepsi and BlackBerry, and were made from green latex, covered with grey fur. Each had a hole in the back of the head for a puppeteer's hand, enabling the mouth to move.
The puppets were shot in front of a green screen and were controlled by puppeteers outfitted in green suits. Steve Clark, lead puppeteer, said: "We're asked to wear these fetching items of fashion for the job, which means we can disappear, giving the illusion of autonomous motion to whatever character we're asked to bring to life."
The aliens were given 3D eyes by the visual effects team in post production, which meant that they had to track the exact position of the puppet's heads throughout the filming.
The campaign has a total media investment of £10m running across TV, digital channels and outdoor.