What are the themes of the play Arsenic and Old Lace?

A delightful combination of the sinister with the
farcical, Jonathan Kesselring's play was so often performed by senior classes in high
school's across the country in the 1950s and 1960s. 

THE
THEATER

The main theme that so often delighted the
audiences at the high schools is the theme of the conventions of the theater. 
Kesselring's presentation implies that the theater reflects life only in absurd
situations.  Mortimer, for instance, claims that drama does not reflect reality; it only
provides entertainment.  Kesselring's play certainly provides entertainment in a most
absurd manner.  In an especially farcical scene, Mortimer describes how a character in a
play he has just seen dies when a murderer captures the hero.  In so doing, he provides
his brother the perfect way to murder
him.

INSANITY

Mortimer's aunts
and Uncle Teddy are all mentally ill.  While the uncle charges up the stairs in the
delusion that he is Teddy Roosevelt, the aunts calmly tell Mortimer to just pretend that
he has not found a dead gentleman.  They say that they hidden the body because it would
not have been nice to have the Reverend Harper to have seen it; besides, they have a
right to their own secrets.  And, they believe that they are doing a service to the
lonely men by giving them arsenic.

Not only is Uncle Teddy
insane, but his grandfather was, as well; for he created some medicines that he tested
on people, to their detriment.  Of course, Jonathan is cursed, also, as he has killed
twelve men.

ALTRUISM

While the
aunts seem charitable as they open their home to people, giving toys to the poor
children, offering lodging for strangers, and providing tea and snacks for the
policemen, they also are killing people in this farce.  But, they are only "good"
Christian Americans as the sisters do not want foreigners in their home, not their
murderous nephew Jonathan whom they have forbidden to come to their house.  It is on
this "charitable" work that the satire lies.