Ironically, ампутант was one of the only words that didn't come from my own head when I was writing the Russian version -- I tried to rely on my own memory and knowledge of Russian instead of using the dictionary (thus the many mistakes!) but I had absolutely no idea how to say "amputee" по-русски. So I looked up ампутация on Russian wikipedia and found the phrase "инвалид-ампутант" there.
Perhaps I could change it to say "...работают вместе с добровольцем-инвалидом. Тот -- американский морпех, у которого правую руку до плеча оторвал взрыв..." How does that sound?
Not everyone has seen "iRobot" (I haven't!). I used Luke Skywalker because he's probably the world's most famous science-fiction example of a biological human who has a robotic arm or leg. (Darth Vader and RoboCop don't count because they are "more machine than man." And Americans are familiar with Steve Austin and Jaime Sommers, the "bionic" television superheroes from the 1970s, but I figured most Russians haven't heard of them.)=> как у Люка Скайвокера or better как у Вилла Смита в фильме iRobot, because Luke had only his wrist cut off with a light saber.
I know they're different, but since I was translating the joke into Russian, I tried to "translate" the gesture, too. But now that you mention it, I guess it's better if the Marine makes the normal American gesture, since the whole point is that he doesn't understand Russian and therefore wouldn't be familiar с русским жестом, называется "фига". Would "он показывает средний робо-палец" be the correct way to say it?солдат широко улыбается и в шутке показывает "фигу" робо-кулаком.
=> Фигу or his middle finger? Those are two rather different gestures.
But anyway, Crocodile, thanks very much for all your help with the vocabulary and grammar!