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:
I love this story about Hirohito sulking because he alone couldn't eat fugu
Chamberlain: Your Majesty is forbidden
C: It's poisonous
H: But everyone else is eating it
C: The poison has been removed
H: OK, I'll have some too
C: It's forbidden
So, what is the truth about the emperor and fugu?