That is something that I kind of miss after selling my 400mm F5.6 lens - it was a monster! Of course, you almost needed a monopod to even think about getting a steady shot (although I got rid of it before I got my K100D with IS, that may have helped, but the CA was unacceptable on the lens)... but it sure did look impressive, especially with the built-in lens hood extended!
I still want to pick up a vintage Zeiss 180mm F2.8 one of these days, another monster that weighs over 3 lbs...
As for that green lens, that looks like a prop from the Buzz Lightyear Astro Blasters ride!