The professor was Hermann Minkowski and the "lazy dog" was Albert Einstein!

Evidence is not clear about how Einstein felt about Minkowski's remark. Minkowski died on 12 Jan 1909 in Göttingen, Germany. Coincidentally Einstein was visiting Göttingen at the time, and a strange note was found above the body: "Who is the lazy dog now?"

Nobody understood what the note meant but police found no evidence of foul-play :-) Inspector Clouseau's deputy wrote this transcription of what the inspector concluded: "No reason at all to suspect anything but natural death, so not wasting time investigating further. The scene is clean. If this was foul-play then the perpetrator must be the greatest genius of our time."