Cadbury broke its own ads — glitchy posters and all — to launch Mystery Bars

Cadbury's senior marketing director Benazir Barlet-Batada wanted the brand to become more 'participative' for 18 to 34-year-olds, building on the Cadbury Inventor platform that since 2019 has drawn about 120,000 people submitting some 90,000 flavour ideas a year.

Two mystery bars launched with deliberately broken media — crinkled bus stop ads, glitchy digital posters, Instagram posts that don't fully load — across OOH, online, social and a Spotify digital audio campaign, with media by Carat. Clues flowed through Cadbury's social channels and mailing list ahead of the bars being unwrapped in October 2022.

No campaign results were reported at press time; the preceding Inventor TikTok push had lifted ad recall 17.9%, awareness 3.7% and purchase intent 4.4%, and the new work tested as one of the brand's best-ever results for brand equity.

In a stunt straight out of Charlie and the Chocolate Factory, Cadbury launched two mystery chocolate bars in 2022 and challenged Britain's flavour detectives to guess what was inside for a £5,000 (almost $6,000) prize — and advertised the puzzle by breaking its own advertising.

With longtime agency VCCP, the creative was intentionally malfunctioning: crinkled bus stop posters, glitchy digital displays, Instagram posts that didn't seem to fully load. The broken-ness was the message — something at Cadbury was not as it should be, and only participation would resolve it.

The campaign ran in the UK until September across out-of-home, online, social and Spotify digital audio, all planned by Carat, with clues distributed through Cadbury's social channels and email list before the mystery flavours were unwrapped in October 2022. It extended the participation playbook of Cadbury Inventor, whose three annual finalist bars reach shelves, with the most recent winner — Crunch Honeycomb — invented by a 19-year-old student.

Glitchy creative embodies 'mystery' instead of merely saying it.

It extends a proven participation franchise: Inventor pulls roughly 120,000 submissions a year.

TikTok over-indexes for the 18–34 target, so a solvable puzzle fits how the audience already behaves.

If you want participation, give the audience a puzzle: broken media turns an interruption into an invitation.

The bars were to be unwrapped in October 2022, with success measured on brand love, brand health and penetration.