Timmy is an average kid that NO ONE understands. His parents are extremely addicted druggies who are very abusive and neglectful. He has no friends. Timmy is a repressed kid who's never been able to live normally. Also, Timmy has shown a tendency to be rather stupid and lacking, even for a 10 year old. He always gets Fs and is unable to deduce things using common sense. Not to say that he's as stupid as Cosmo or his parents, but he's definitely lacking in the common sense department. Anyway, there is a reason why Timmy is like that.
When his mother was pregnant with him, being the irresponsible, reckless idiot that she is, she did drugs. And the father, being even stupider, did drugs with her. So, Timmy grows up really messed up and sheltered. He has difficulty making friends or studying. Timmy's parents see Vicky as the perfect babysitter, because they applaud Vicky's abusive behavior toward Timmy. They think that Timmy is a slow, hopeless idiot who will not understand anything. So, when they're not around to abuse Timmy while loaded on drugs, then they've still the perfect backup ready. Timmy's parents are extremely drugged up on crack and they abuse him and, due to this, Timmy grows up an extremely socially awkward kid and has extreme difficulty making friends.
Crocker's mother isn't alive. She never was. She was dead since he was born. In fact, she died in giving birth to him. That's why his father abused him like crazy. But Crocker can't bear with the fact that it was essentially him responsible for his mother's death. That's why he imagines his mother there with him and hates her for not being alive with him; for not coming and making everything better when his daddy beat him; for leaving behind him as the burden of the family. And there is a reason why Crocker became a teacher: he longs for his childhood so badly, that he wants to be among kids, because they remind him of the childhood that he never got to have. And he made up some friends