Hamlet, Stella Adler (2017), CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
Hamlet and the Ghost, Internet Archive Book Images (1917), No restrictions, via Wikimedia Commons
The ghost of Hamlet's father (literally) haunts the narrative. He appears dressed in military regalia, figuratively illustrating his success against international forces such as Fortinbras and his own demands for Hamlet to use violent means to avenge his death. A potentially interesting autobiographical article on the relationship between Hamlet Jr. and Sr. can be found below. I'd recommend starting at page 72 and skimming for relevance.
Hamlet and his Father's Ghost, William Blake (1806), Public domain, via Wikimedia Commons
The idea of acting or "playing" truth to power is familiar beyond simply Shakespeare. Generally, it is the fool or jester role that is able to navigate and criticize the convoluted world of nobility. One may recall Feste in Twelfth Night as an example:
OLIVIA Take the Fool away.
FOOL Do you not hear, fellows? Take away the Lady.
...
FOOL Good madonna, why mourn’st thou?
OLIVIA Good Fool, for my brother’s death.
FOOL I think his soul is in hell, madonna.
OLIVIA I know his soul is in heaven, Fool.
FOOL The more fool, madonna, to mourn for your
brother’s soul, being in heaven. Take away the fool,
gentlemen.
The players are distinct from Feste, however, in that they are unknowingly speaking truth to power. Indeed, it is Hamlet who uses their talents to perform what he believes to be true and gauge the reaction of Claudius to their rendition. How much the players are aware and actively consenting to be a part of this (potentially rather dangerous) conspiracy is an open question for actors to consider...
Hamlet Play Scene, Harold Copping (1897), Public domain, via Wikimedia Commons
(left) Hamlet, Horatio & the Grave Digger, William Mulready (1810), accessed via NYPL
The gravedigger's presence represents a brief moment of clowning before the murderous spree that takes place in act 5. Fittingly, the clownery is from within Ophelia's grave, and the entire exchange has a morbid energy to it despite the humor. I also find the gravedigger a refreshing reminder that there is a world outside of the royal family's interpersonal drama; one that frankly, has more pressing matters to attend to, like digging graves.
Singing a merry tune while digging is our gravedigger's introduction in this cut, linking the gravedigger figuratively to Ophelia, whose grave he is digging, even without him realizing it. Given the importance of music to this scene, I've included an (admittedly, rather odd) music video to the right that I think similarly plays with the line between humor and morbidity. Happy to discuss my thoughts about this further in-person!
The ghost and player king pairing seems fairly obvious, though I am curious to see how Claudius's reaction to the play may be heightened by this casting decision. Additionally, Hamlet's reaction to the players' casting could be interesting to explore as well.
I find the incorporation of the gravedigger to be most interesting in this casting arrangement. It seems to me as though the gravedigger literalizes what Hamlet Sr.'s ghost is doing to Hamlet: preparing a grave for him to jump into.