Okey...
My parents went to see 'Wargames' just after I was born, so it has always kind of been 'my movie' in a way.
In that movie there is a scene in which 2 computer nerds tell matthew broderick about the 'back door' into WOPPA. And one nerd call the other 'Mr Potato Head'.
When I was about 14 I started using Mr Potato Head to fill in online forms when i didnt want to use a real name, and it became an online handle.
Then in yr 10 I got suspended from school for hacking, and my Dad made a joke about Wargames, quoting the Potato Head! Mr Potato Head!" bit.
It seemed like such a bizzare coincidence to me - that i'd been using it already without even remembering that it was the name of some computer nerd in 'my movie' (and I was obviously a computer nerd too). Anyway I have used it ever since, except I ocassionally shorten it to Potato, as is the case with bluelight.
Also it's the name of an excellent episode of Black Adder.