You might have read recently about the Eddy Grant/Gorillaz case; Grant claims that the Gorillaz track Stylo bears a melodic resemblance to his 1982 song Time Warp.
Have a listen for yourself and see what you think, then vote in the poll at the bottom. The alleged similarity can be found at 0:42 (in Stylo) and 0:18 (in Time Warp).