According to Wikipedia
Fugu is also the only food the Emperor of Japan is forbidden to eat, for his safety
This information comes from a Forbes article "Killer Foods":
The fish remains the only delicacy denied the emperor – too risky.
This seems a bit fishy to me, so doing a search in Japanese, the best I could come up with was this anecdote, with my translation interspersed:
昭和天皇が自分だけフグ食べさせてもらえなくて拗ねられた話大好き。 I love this story about Hirohito sulking because he alone couldn't eat fugu 侍従「陛下はだめです」 Chamberlain: Your Majesty is forbidden 陛下「なんで」 Hirohito: Why? 侍従「毒があるので」 C: It's poisonous 陛下「みんな食べてるじゃん」 H: But everyone else is eating it 侍従「毒抜きしましたので」 C: The poison has been removed 陛下「じゃあ私も」 H: OK, I'll have some too 侍従「だめです」 C: It's forbidden 陛下「なんで」 H: Why?
So, what is the truth about the emperor and fugu?