Sam Mendes, in a DVD commentary referred to a scene in the Bond movie Skyfall as the 'Hamlet scene' because it involved three actors who'd all played Shakespeare's Dane: Ralph Fiennes, Rory Kinnear and Ben Whishaw.
I was reminded of this when listening to James McAvoy being interviewed on Radio 4's Front Row about the new X-Men film recently. McAvoy gets screen time with Patrick Stewart and the presenter John Wilson asked if they discussed playing Macbeth to which McAvoy said they did. He then went on to point out that they weren't the only two actors in the film to have played the Scottish King on stage as Ian McKellen has also taken on the part and Michael Fassbender is just about to in a film version.
It is further significant because McAvoy and Stewart plays the younger and older version of the same character in the film as do Fassbender and McKellen.
Now I'd love to know if Fassbender asked for advice and what McAvoy and Stewart discussed. I'd also be curious to know if anyone can beat four actors appearing in a film who've all played the same Shakespeare character?
As to the collective noun I reckon you'd have a worry of Hamlets and an ambition of Macbeths but I'm sure there are far, far better words.
First, much better, suggestion via Kathryn on Twitter is a dither of Hamlets