Daddy's Masculinity (Situational Irony)
Mommy praises Daddy for his masculinity when he decides to go to open the door when "they" arrive. She is excited that he is being decisive and direct by taking charge of the situation. This in itself is ironic, because Daddy is only going to answer the door because Mommy has pressured him to do so. When he has a sudden change of heart and doesn't want to answer the door, Mommy gets angry with him and calls him a "woman," which is ironic because it directly contradicts what she was saying moments ago. Mommy is very manipulative of Daddy, but then she belittles him, an abusive dynamic that ends up being pretty ironic.
Living off other people’s money (Situational Irony)
Grandma criticizes Mommy constantly for living ofd Daddy’s money, calling her own daughter a gold-digger. Ironically, however, Grandma is also living with them, and so is benefitting from the very thing that she is criticizing her daughter for doing.
The Young Man is Bumble's Twin (Situational Irony and Dramatic Irony)
While it is only referred to obliquely, the audience is led to understand that 20 years prior, Mommy and Daddy adopted a baby from Mrs. Barker's adoption agency (even though none of the parties involved can seem to remember one another). The baby that they brought home—a "bumble" of joy, as Grandma calls it—was insufficient and so Mommy and Daddy gradually disfigured it, before it eventually died. They then went back to the adoption agency looking for a new one.
While no one knows who Mrs. Barker is—even Mrs. Barker doesn't know why she's there—it eventually becomes clear in the play that she's there to make up for Mommy and Daddy's botched adoption. When the Young Man shows up, he is the perfect replacement for their old son. The irony, however, is that the Young Man is the original baby's twin, and the violence that the original twin suffered has left the Young Man "incomplete" and incapable of love. Mommy and Daddy thought they could return their old baby in exchange for a new one, but the damage they did to the first one has done damage to the Young Man, its replacement. There is a tragic irony in the fact that Mommy and Daddy's violence comes back to haunt them.
The Young Man is Bumble's Twin (Dramatic Irony)
The fact that the Young Man is the original "bumble"'s twin is an example of situational irony, because Mommy and Daddy are welcoming a victim of their own violence into their home. It is also an example of dramatic irony because they have no idea that he is the twin of the first child they adopted. They think he is just a random stranger who has wandered into their house to make their lives better. Thus there is a dramatic tension between the fact that the audience knows that he is the twin of the son they brutalized, and the fact that Mommy and Daddy are blissfully unaware.
