The campaign by Mother London features new TV spots supported by video on demand, cinema, outdoor and print activity.
The TV ads depict the puppets fighting over the last can of Diet Coke in the fridge, executed in a humorous way in order to demonstrate the "lighter side of life".
The brand is also launching three new pack designs to advertise an on-pack promotion for make-up brand Benefit.
The cans will contain a promotional code for a limited edition make-up pack, redeemable when spending more than £20 on the Benefit brand.
The promotion is also supported by a 10-second ad called "get glam" and outdoor, digital and PR activity.
A new Facebook app, www.dietcokegetglam.co.uk, will feature the best "get glam" looks consumers can create with the make-up packs and chat to friends via a "glamming together" video chat tool.
Zoe Howorth, market activation director at Coca-Cola GB, said: "The 'Love it Light' campaign returns for the fourth time in 2012 featuring the distinctive Diet Coke puppets. The campaign demonstrates the brand’s light-hearted attitude and appeals to young, fun-loving women.
"Elsewhere, we're delighted to be partnering with Benefit to inspire consumers with the latest beauty looks and reward them with money-off at www.benefitcosmetics.co.uk."
In May last year, Diet Coke partnered with Yahoo to create a digital fashion channel called Style it Light as part of the wider 'Love it Light' marketing push.
Follow Loulla-Mae Eleftheriou-Smith on Twitter @LoullaMae_ES