You should have looked him straight in the eyes, and depending on the color of his eyes, said one of the following:
- If his eyes were brown, you should have said, "I thought so.... Brown eyes... You must be filled to the top."
- If his eyes were NOT brown, then you should have said "I would have sworn your eyes were brown the way you are talking..... I guess you just aren't filled to the top yet."
Hopefully it wouldn't take him too long to "get" it.....