The ad, which made its debut on January 23 during the 'Celebrity Big Brother' finale on Channel 4, has demonstrated the true "viral" nature of word-of-mouth and the internet.
A visit to YouTube shows that the "official" version of the ad has been viewed nearly 1.9m times -- given the numerous other uploads of the ad on YouTube alone and those appearing on other web video sites, Cadbury's claim of 4m may not be an exaggeration.
The ad, which was created by Fallon as part of a £3.7m campaign, has also drawn praise from some unlikely quarters. American rapper Kanye West has posted a link to the video on his blog; US celebrity blogger Perez Hilton described it as "super-cool"; and serial "Twitterer" Stephen Fry added to the fanfare on social networking site Twitter.
The one-minute commercial has also inspired a spoof by Lily Allen and Alan Carr on Channel 4's 'The Sunday Night Project'.
As if all that publicity were not enough, Cadbury has also partnered with mobile operator Orange (also a Fallon client) to give away the commercial's soundtrack as a mobile ringtone. This was downloaded 125,000 times in the first 11 days.