Well, everyone's aware that George Bush suffers from S.P. Word has it that he forgot almost half of the State of the Union address and had to wing it. This is why he holds so few press conferences, fewer than any other president ever. He is honestly afraid of the spotlight. The whole WMD thing must be giving him serious panic attacks! I feel for old W.
Also, Dick Cheney's a major introvert, as well. During the whole 9-11 thing, word has it that he became agoraphobic and wouldn't come out of his lavishly furnished Pentagon bomb shelter for days. That quickly passed, thank god! Lord knows we need him as v.p!