As with many of Shakespeare's plays, this tragedy involves many characters who intentionally disguise themselves or pretend to be what they are not. What is interesting about this play however is that there seem to be characters who disguise themselves intentionally for good reasons, and those characters who do so for bad reasons. Note what Kent says in Act I scene 4, having been banished, which explains his decision to disguise himself:
If but as well I other accents borrow
That can my speech diffuse, my good intent
May carry through itself to that full issue
For which I razed my likeness. Now, banished Kent,
If thou canst serve where thou dost stand condemned,
So may it come they master, whom thou lov'st,
Shall find thee full of labours.
Even though Kent has been wronged by his master, he determines to "raze his likeness" out of his devotion to Lear in his desire to serve him still, albeit in a very different capacity. This "good intent" behind his disguise is of course sharply contrasted with Regan and Goneril, who pretend to be devoted daughters for the wrong motives. Interestingly, we could argue that the one character in the play who doesn't disguise herself or pretend to be what she is not is actually Cordelia. Perhaps the theme of disguise and deception paints a very harsh picture of the world, as those who are unable to disguise themselves seem to be left vulnerable and exposed to the machinations of those who can.