The channel, owned by Turner Broadcasting, wants Fever to target four- to eight-year-olds in an experiential and media relations campaign across the country.
The appointment comes before the launch of a new incarnation of the popular programme, Ben 10 – Omniverse, which premieres in October.
Fever was hired after several meetings with agencies earlier in the year.
The agency will deliver an awareness and brand-building PR campaign, including integrated experiential, social and media relations activities.
Fever begins the campaign on 4 August with events at nine UK shopping centres, culminating in a Guinness World Record attempt on 29 September at Bluewater.
Children will be asked to each bring a Lego brick to the event to build a giant alien. Fever hopes that 100,000 children will take part, breaking the world record for the number of people building a Lego model.
Fever will report to Turner Entertainment’s newly appointed director of PR and comms, Charlotte Chisnall.