Back in 2009 the Linux mascot, Tux, was temporarily replaced by Tuz. Tuz was a Tasmanian Devil character and the use of the logo was used to promote this endangered animal that's nearly extinct in Australia. Tuz replaced Tux in the Linux 2.6.29 kernel, but with Linux 2.6.30 there was the return of Tux. Now with the Linux 3.1 kernel that's a proposal (RFC) for a new Linux kernel logo.
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This new logo was proposed just this weekend and the current discussion to see whether it will be accepted for Linux 3.1 can be found in this LKML thread.