Being of a plagaristic nature. To claim authorship (especially Copyright) of a work. Particularly applicable to a person who refutes the claim of plagarism in the face of undeniable evidence.
Adam: I totally made up Superman dude!
Steve: You seriously didn't man. You weren't even born when Superman was created!
Adam: I'm telling you, Superman was my idea!
Steve: You are such a f*cking Karl Thomas!