I have been reading this book now for a while, very sporadically, on Commedia dell’arte by Giacomo Oreglia. It’s an old book, but it has lots of information about the characters throughout the centuries. The main descriptions are the ones for the original characters, which might be why I and Hadleigh disagree whether “The Fool” is Harlequin or Brighella (to the left).But I’m going to follow the books description here, to start of with.

Harlequin: the “second servant” (Brighella is the first).
His personality was to start of with very simple; he was stupid and constantly hungry. It’s now more defined though, he is gullible but still suspicious, cowardly but still obtrusive and is a mixture between naive and cunning, grace and clumsiness.
Opposed to Brighella, Harlequin doesn’t move the plot forward, but he makes the rhythm for it (which it says here is a far more complicated task). Therefore he is always moving, and very acrobatic. -->
Brighella: full name is Brighella Cavicchio, where “briga” means intrigue and “cavicchio” means pretext or excuse.
This is because Brighella always finds his way out of trouble. He is shrewd, cynical and without hesitation. He is a master of disguise and deceiving.
His purpose is to always keep the plot going forward with intriguing, mainly for his own benefit and pleasure. He can stop certain weddings and bless others, he flatters and plants suspicions and make talismans and love potions and whatnot.
He plays a whole lot of roles, not only the servant; soldier, innkeeper, executioner, thief etc.
And therefore I think that Brighella is more fitting than Harlequin, although Harlequin is the most popular and famous, and probably a lot easier for a young audience to recognise.
So we’ll se.

