Isn't Idéfix also a pun - it is in English; Idée fixe, psychological term borrowed from the French, means "fixed idea"; an obsession or persistent delusion or belief.

I had kind of been assuming the translator couldn't add puns in the names because they were ALL puns already, they could just make them worse. Although I couldn't figure out Caius Bonus's pun, I'm sure there is one.