Subverted: It initially seems like Bob's dad is never about, but then we see him and his father having a good time together, and showing that they are quite close. Apparently the dad was just at work all this time or something.
Double Subverted: Until the villains kill the dad.
Parodied: All the family photos have Bob's father cut out from them.
Zig Zagged: Perhaps because his work is seasonal, sometimes Bob's dad is at home and always there for him, and other times his dad is absent for long streches and completely out of touch with Bob.
Averted: Bob's dad is always there for him, regardless of what happens.
Enforced: One of the writers was born after his father died (or his parents were divorced), and he decides to apply this aspect of his life to a character.
Lampshaded: "Mommy, what happened to Papa?"
Invoked: Bob's dad purposefully walked out of his son's life, perhaps because he thought he would be a bad influence on Bob.
Exploited: The villain tries to use Bob's father's absence to induce a breakdown in Bob.
Defied: Bob's dad goes to great lengths to be a part of his son's life, regardless of what the world throws at him.
Discussed: "Where is Bob's father? It's almost scary that we've never seen him."
Conversed: "Why doesn't that kid have a father? Are we to believe he was adopted or what?"
Despite him being a kid, Bob's dad is never brought up in any way, shape or form, leading the audience to believe that this was the case.
Bob's family is mentioned but never seen. Bob constantly tells his friends how much he loves his mother and siblings, but does not mention his father even once.
Plotted A Good Waste: At first, most characters' fathers are not shown because they are at work. The writers eventually decide to show most of them except Bob's father, because they feel that there should realistically be at least one single-parent family in the cast.
Played For Laughs: Bob's father is a deadbeat who still lives nearby, but goes to great lengths to avoid his ex-wife and son.
Played For Drama: In a Father's Day episode, most characters are shown bonding with their fathers, and everyone sympathizes with Bob, who feels left out because his father is dead.