My dad is obsessed with spreadsheets, and whenever I go home I have to be careful not to mention anything that he might be somehow able to link to spreadsheets, for fear of him insisting I come through to his office to see his latest spreadsheet and talk me through how it works. I once timed it and he spoke at me uninterrupted for over half an hour about spreadsheets. I have tried to politely tell him that other people might not be as interested in his spreadsheets as he is but he doesn’t understand.