Same Difference

Are you one of the people that say this? Do you also say "stop" when you mean "go", or "black" when you mean "white", or "potato" when you mean "tomato"? For those of you lucky enough to not know what I'm talking about let me elaborate. I'm sure most of you have heard someone say "same thing" when someone else is talking about two similar items, events, ideas etc. However, sometime around the 8th grade I started hearing people use "same difference" in the place of "same thing" (yes it bothered me then also). Every time I hear someone make this statement I feel the need to point out how illogical it is, but the speaker never seems to care. If you are talking about two like items how can they have the same difference? Does the word different all of a sudden connote likeness? It makes NO SENSE. I must not have received the memo that stated you can substitute any word for any other and still expect people to understand you. The only possible way that two items could have the same difference is if you were comparing them to a third item. For instance two circles have the same differences in relation to a square, but have the same qualities/similarities in relation to each other. Again, if there was a memo sent out and I missed it I apologize to everyone in advance.