Subverted: Al tells Bob that he didn't need to do anything to gain his approval - which confuses Bob, as he started doing things to improve his life for his own sake.
Double Subverted: However, as Bob really analyzed his behavior, he realized that subconsciously, he did do those things because that's what Al wanted.
Parodied: The workaholic or working-class son Bob tries to win the approval of his high-culture or art-focused father Al. (A good example is a Monty Python sketch called Working-Class Playwright.)
Zig Zagged: ???
Averted: Either Al is open with his approval of Bob, or Bob feels no need to prove himself.
Enforced: "I know a situation to change Bob's unruly behavior: have him earn the respect of his dad."
Lampshaded: "Why is it that no matter what I do he'll never say 'I love you' or 'I'm proud of you'?"
Bob doesn't feel he needs to win Al's approval, but a third-party insists he must.
Al's father was like that with him, and he credits the emotional distance for allowing him to succeed. So, he does the same thing with Bob.
Exploited: Al is a Jerkass who deliberately maintains a facade of emotional distance so Bob will do things for him.
Defied: "Ah, screw it. I'm proud of you, son."
Discussed: "Seriously, it's impossible to please your parents, especially if it's your dad."
Conversed: "I'm not going to wait another 2 seasons until Bob gets the respect he deserves from his father!"
Al dies without ostensibly letting Bob know that he loved him. This tears Bob up inside and causes him to lash out at everyone and everything.
Alternatively, Al lets Bob know that he really doesn't care about him, which warps Bob psychologically.
Alternatively: After had for so long tried to gain Al's approval, Bob becomes more bitter and bitter about his father. When the day comes that Al finally express his approval, it's too late for Bob and instead of satisfaction Bob feels bitterness and even spite for the approval.