Think about it for a minute if you would, Dogberry is in charge of Messina's night-watch, hardly a role that would be given to a genuine idiot. The likely explanation is that Dogberry developed his quirky and 'idiotic' persona as a ruse early on in his career and kept it up to fool the criminals of Messina. So with that in mind maybe the watchmen overhearing Don John's drunk henchman was a well planned Batman Gambit by Dogberry to get the truth of the plot without Don John realising it.
Dogberry only seems like a fool. Most of it has to do with the way he mixes up complex words (i.e. confusing perdition with redemption). However, he and his officers managed to unravel Don John's plot which had taken in "smarter" characters.
His trouble with vocabulary makes perfect sense if Italian was not his first language. Being bilingual means he might have to translate everything in his head (i.e. Leonato says something to Dogberry, Dogberry translates the sentence into, and crafts his reply in, his native tongue then translates his reply back to Italian). Language can be affected by emotion too; he was quite piqued when relating that Conrade had called him an ass that his sentence was "... do not forget to specify, when time / and place shall serve, that I am an ass" instead of "... do not forget to specify, when time / and place shall serve, that I was called an ass".
Also, learning a new language later in life can "lead to better memory and sharper thinking
".
- The 2017 Globe adaptation casts Dogberry as an American film-maker in early-20th-century Mexico, playing him this way. It's brilliant and hillarious.
In the quarto version of Much Ado, Leonato's wife is a ghost character named Innogen — awfully similar to Imogen, the slandered princess in ''Cymbeline'' whose husband is named Leonatus. Apparently the Leonati still haven't gotten over their "my wife/daughter is an unfaithful slut and she should die" complex...
