Prince Hal

In the two plays, the diminutive "Hal" is only ever used of the prince, not of any of the other characters named "Henry". It is only one of the several versions of "Henry" used. In fact the prince is variously referred to in the plays as "Hal", "Harry" and "Harry Monmouth", but never as "Henry". Only Falstaff and Poins ever call the prince "Hal", and Poins does so only twice. In the two plays, Falstaff does so forty times, even hailing him as "King Hal" at his coronation.

In Part 1, the name "Harry" is most commonly used to refer to Harry Hotspur, who is set up as the dramatic foil of the prince. The prince himself is typically called "Harry" when the two are being contrasted. In Part 2, "Harry" is most commonly used when he is being compared to his father, notably at the end by Henry V himself when he refers to the Turkish tradition of killing a newly installed king's brothers, saying that his own brothers should not worry, as "not Amurath an Amurath succeeds,/But Harry Harry". In Henry V he is never called Hal, only Harry. His official royal name "Henry" is only used once, in the play's final scene, when he tells his future queen Katherine that "England is thine, Ireland is thine, France is thine, and Henry Plantagenet is thine".

There has been longstanding debate about the character of Hal in the two Henry IV plays, particularly concerning the extent to which Hal's riotous and rebellious behaviour is authentic and to what extent it is wholly staged by the prince for effect. The portrayal of Hal as a son in conflict with his father derives from stories that circulated in English popular culture before Shakespeare. These had previously been portrayed in the anonymous play The Famous Victories of Henry V, in which Hal's criminal and riotous behaviour is depicted as entirely unfeigned. In Shakespeare's plays Hal has soliloques in which he says that he is self-consciously adopting a wayward lifestyle to surprise and impress people by his later apparent character transformation:

I know you all, and will awhile uphold
The unyoked humour of your idleness:
Yet herein will I imitate the sun,
Who doth permit the base contagious clouds
To smother up his beauty from the world,
That, when he please again to be himself,
Being wanted, he may be more wonder'd at.

In Henry IV, Part 2, the Earl of Warwick suggests that Hal is fraternising with low-life characters to learn about human nature. He is "studying his companions" almost like learning a foreign language, which would include learning vulgar and offensive words, but only "to be known and hated".