Sullivan, who is currently the strategic director across Coca-Cola at Vizeum UK, and Kay, new-business director at Fallon, will be jointly responsible for the day-to-day running of the venture.
The appointments come after a strong first year in business and the success of the Tate Collections campaign.
Sullivan said: "The best work nowadays is when creative and media ideas occur in collaboration -- rather than in isolation or when one follows the other. It is so much easier to achieve this working on the inside, rather than within a separate entity."
In addition, Hyper, the digital joint venture between Fallon and Naked, is expanding with the addition of eight members to the team under the leadership of Brad Fairhead and Tom Johnson.
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