Super Luigi: I read that "igiwalui" thing in Nintendo Power. Personally, I don't believe it... I've never seen "igi" used to mean "someone." But then again, I've only been studying Japanese for a year...
Hinopio: In Japanese it is in fact "waruigi", but pronounced "waluigi" because R's are pronounced like L's most of the time. At first I thought Waluigi's name was a clever combination of "Luigi", "Wa" from Wario, and "warui" (meaning "bad"). Now with this "igiwalui" explanation in Nintendo Power, I'm not so sure...