The tie-up will see Kellogg brand icons such as Frosties' Tony the Tiger and Rice Krispies trio Snap, Crackle and Pop replaced by Cartoon Network favourites including Johnny Bravo and the Powerpuff Girls.
The six-figure online campaign will see a microsite launched next week at cartoonnetwork.co.uk/kelloggs. The site acts as a front page for a Johnny Bravo site and a Powerpuff Girls site. All activity will run for three months.
Games from both brands will feature on the site, alongside e-cards and competitions.
Buttons and banners across the site will encourage users to click through to the Kellogg area. A TV ad running on Cartoon Network's cable and satellite channel will back the web site.
David Walker, marketing operations controller at Kellogg, said: "The characters are very popular and this activity will open up important opportunities for us."
Mindshare's sponsorship consultancy, Broadmind, negotiated the deal.