Family Guy is known for its clever use for satire. In this particualar episode, Stewie appears on the side of his mom's bed and seems as if he needs her urgently because of the use of his mom's first name which is Lois. After Stewie screams her name for the twenty-seventh time, she answers in a frustrated tone. Surprisingly, Stewie replied, "Hi."
This is an example of situational irony because when Stewie screams his mother's name so much, viewers tend to think that he wants something very important like he needs his diaper changed. Instead, just to annoy her, Stewie says, "Hi". It's unbelievable how simple and clever the transition from Stewie saying Lois to mama. This is the reason why the writers of Family Guy get so much praise for their work.