Ut cachinnis dissolvatur, torqueatur rictibus!
I think it sounds very nice in Latin, that in addition to its agreeable meaning.
Apparently, in many translations of the book it is still in Latin.
There is a great sounding Russian translation by Elena Kostioukovitch:
Всем полопаться от смеха, скорчиться от хохота!
(roughly: vsem polo'patsia ot sme'ha, sko'rchitsia ot ho'hota!)
Some googling produced an English version in an article by Douglass Parker which I could not fully identify with:
May he dissolve in laughter, may he be racked with guffaws!
More googling produced a Turkish version:
kahkahalarla gülünsün, gülmekten katılınsın
I do not know any Turkish (just heard some), but phonetically it is very nice (if I read it anything near correct).
Does anybody know translations of this line to English or other languages?
Or do you want to produce your own version? Thanks!