Disappeared Dad: He decided that he didn't want to be in his daughter Jenny's life anymore and just sent child support.
Dreadful Musician: He can definitely play the piano well, and turns out to have a surprising proficiency for writing childrens' songs, but most of his actual jingles are so bad that it makes you wonder how he was ever able to make a living (to say nothing of a living in Malibu) off of it.
Dude, Where's My Respect?: His family does nothing but insult him, his career and his lifestyle despite him being incredibly successful as a musician (The quality may be questionable, but he's still really successful.) and having every right to live his life as he sees fit.
Everyone Has Standards: Charlie found there were lines even he wouldn't cross, such as in the Christmas episode where he refused to sleep with a woman that was possibly his sister. As Rose quipped, "It's a Christmas miracle!"
He also refuses to sleep with teenage girls, as shown with his refusal of Berta's granddaughter's (played by Megan Fox no less) advances.
Flanderization: Charlie became an even heavier drinker and an even bigger Jerkass. Was flanderized into a hard drug user after his death, though this may have been part of a large Take That aimed at Charlie Sheen.
I'm not saying I hate you, but if I did, it might have something to do with the fact that you're a narcissistic bloodsucker who drove my father into an early grave, after which you married a succession of men who couldn't care less about Alan and me, which was just fine with you 'cause you... looked at us like a couple of dancing monkeys you could just haul out whenever it suited you! And when it didn't, you sent us off to boarding school or camp or that kibbutz in Israel, where we got beat up 'cause we weren't even Jewish! And now... now you show up here every chance you get to lay a guilt trip on me for not appreciating my cold, lonely, loveless childhood!
Real Life Writes the Plot: After his falling out with Chuck Lorre, Sheen's Character is killed off in a very unglamorous way and manages to undo his potental Character Development in the Trip he took with Rose at the end of Season 8.
Aesop Amnesia: After Walden's ploy to find a woman by pretending to be someone he's not completely blew up in Walden's face, despite Alan's warnings, Alan seems to have completely forgotten these events ever happened in Season 11 and pursues Lyndsey and her fiancée's sister, Gretchen, using the false identity of "Jeff Strongman."
And like Walden, Alan ends up losing it all. For now.
Bitch in Sheep's Clothing: Alan is the kind of guy who has spent his whole life living by an arbitrary morality, and is now mad that he hasn't reaped the rewards he thinks he deserves for it. Yes, life hasn't treated him all that well, but a lot of that is because Alan is a spineless doormat; he is incredibly resentful against his brother, who lived in hedonistic revelry that Alan secretly wanted himself, but never allowed himself to go for because he thought that the universe would automatically reward him for his passive aggressive nice guy act. In the last few seasons of the show, however, he seems to have realized this, and consequently has relinquished all pretenses of being a Nice Guy.
Not So Different: Alan likes to act like he's better then Charlie because he got married and had a kid instead of having endless casual sex in various ways, but while he doesn't have as much sex as Charlie(or with as many women), Alan has quite a bit of casual sex and has cheated on women several times and done some other morally questionable stuff throughout the series.
Born Unlucky: Despite all his faults, one cannot deny that Alan was born with some kind of curse hanging over his head.
Butt Monkey: Try and name one episode where something bad doesn't happen to Alan in some way. Go ahead, try it.
The Cassandra: He repeatedly warns Walden about Rose, and is eventually proven right.
A Date with Rosie Palms: Very often. Charlie's even caught him having sex with a vacuum, he admits to masturbating before dates to get the right enthusiasm out of women, and once masturbated seven times in several different locations just to use up pills before they expired (eventually getting arrested when he was caught in a movie theater).
Deuteragonist: From Seasons 1-8. In Season 9, one could argue that Alan is the main character (at least for the first half of the season), but by Season 10, Walden is the main focus; in Season 11, he and Walden have roughly equal amounts of importance.
Flanderization: Into a Jerkass that makes no attempt to find a place for himself and sponges off Charlie (later Walden) without remorse for his actions. Combine that with the recent levels in dumbass he's been taking, and that's essentially Alan's new characterization.
Holier Than Thou: He looks down on pretty much everything Charlie does that isn't an age appropriate relationship.
Hollywood Dateless: He's a very, very, very strange case. Alan finds himself having sex with a woman every two episodes or so, but his bad luck with maintaining a relationship stems from his crippling insecurity and neediness, Mommy Issues, and his tendency to gravitate towards emotionally damaged women.
Kavorka Man: He's managed to hook up with a legion of attractive women, despite being broke, a Cosmic Plaything and not particularly good-looking, including mothers Judith and Lyndsey, Brainless Beauty Kandi, Melissa, and countless others. Nearly all of these have ended in disaster, however.
MD Envy: He is a chiropractor that is constantly made fun of for not being a "real doctor."
Mistaken for Gay: Sometimes with Charlie, but it turns into a running joke with Walden from Season 9-on. Every woman that learns they live together seems to think they are a couple.
Mama's Baby, Papa's Maybe: Played with. It's implied that Jake might not even be Alan's son; Charlie can't help but notice how much the exterminator, water deliveryman, and mailman all resemble Jake...
No Pregger Sex: He claims the best sex he ever had with Judith was during the time she was pregnant with Jake, which explains his offbeat pregnancy fetish.
No Respect Guy: If Alan is given any amount of praise whatsoever from his family, it's gone or forgotten by the next episode.
The Unfavorite: He's gotten flanderized into this over time, with recent episodes having Evelyn being repulsed by the very thought of Alan.
Ungrateful Bastard: He shows brief glimmers of this throughout the entire series, but it's more prevalent in later seasons.
Unsympathetic Comedy Protagonist: Gets flanderized into this around Season 7-8, although how bad he acts depends on the writer. It goes from such despicable acts as cheating on Lyndsey (who actually loves him) with Melissa for meaningless sex and then getting away with it scot-free, to feeling remorse for stealing Judith's diamond earrings to purchase Lyndsey a birthday present. Really, Alan zig-zags between this status in Seasons 7, 8, and 9, but by 10, he's definitely become a Jerkass.
He and Charlie were this when the latter was alive and they weren't fighting about something.
Yank the Dog's Chain: On numerous unfair occasions, most notably when he found happiness with Kandi and moving into a condo, only for Kandi to leave him a few months later, keep the condo, and have the alimony checks for Alan continue, this time for two ex-wives.
Like Uncle Like Nephew: Jake had quite a bit of success with women just like Charlie did. In high school Jake had a threeway with two girls that he likely lost his virginity to, and slept with his tutor, Zoey's slutty neighbor, Missy (who had a boyfriend), his older girlfriend Tammy, and then Tammy's daughter. Charlie would have been proud.
If some of Jake's throwaway comments to Alan mean anything, the list might be even longer.
The Pigpen: Combine this with being stupid and an eating machine, and that's Jake in a nutshell.
Pet the Dog: He was genuinely sad for Charlie that he and Chelsea broke up.
Put on a Bus: Starting Season 11. He likely isn't coming back (barring the role being recasted), due to Angus T. Jones having decided to largely give up acting in the wake of becoming a Born-Again Christian, and limiting himself to stage work and occasional independently-produced Christian films.
The Ace: She's her father's daughter alright, when it comes to women, and has a more easy-going demeanor in general.
The Alcoholic: To the point where she tries to cure a hangover with vodka.
Chick Magnet: Seriously. She picks up a girl in a bar that isn't a lesbian without revealing that she herself is a lesbian.
And already has managed to sleep with non-lesbians, such as Walden's mom Robin, Lyndsey (as part of a threesome with Lyndsey's boyfriend) and Lynda freakin' Carter. Walden even calls it the "lesbian zombie" virus.
Karma Houdini: Outside getting her ego stung slightly by the odd dry one liner, she has gotten away with taking Alan for everything (though that was also Charlie's fault), as well as constantly hurling abuse at him, trying to control his life and being a full on Jerkass to him for almost a decade as well as treating Herb and Jake like crap and indirectly interfering with Charlie's life as a result. It only seems to be set in stone now she has been Put On The Bus.
Mama's Baby, Papa's Maybe: The paternity of her daughter Milly is called into question before the girl was even born (as Milly was conceived around the time Judith and Herb were separated whereupon she and Alan had a brief affair). Moreover, everyone (except Herb) can see that Milly resembles Alan a great deal, causing Judith a great amount of aggravation. The question itself is never actually answered, but it really does look like Alan is the biological father.
Comedic Sociopathy: She has yet to be prosecuted for stalking and murdering Charlie, despite basically confessing the latter to the assembled crowd at his funeral.
Demoted to Extra: With Charlie dead, it's very unlikely that Rose will ever play a major role in the series again, although it has been shown that she is now stalking Walden.
Flanderization / Took a Level in Jerkass: She originally gave off a sweet and innocent vibe to conceal her true nature, but in later seasons, becomes a full-on Ax-Crazy bitch who takes delight in doing nasty things to get her way, and has no problem letting anyone know.
Killing Charlie definitely cemented this status.
Flower Motifs: Her clothes embroidered with flower patterns, topped with her name.
Jerkass: In her own way, although she may not seem like it at first glance. And she did murder Charlie. But, to be fair, he did cheat on her and as Berta states, "Never cross a crazy woman." She also stalked Walden and had her ferrets attack Walden when he dumped her.
Karma Houdini: It's heavily implied that she killed Charlie. Plus all of the stalking over the years.
Bungled Suicide: He tried to drown himself in the ocean outside of the beach house after his wife left him, but apparently didn't realize the water would be so cold.
Butt Monkey: He's still much better off than Alan, but has started to verge into this territory recently.
Characterization Marches On: Around the time when Walden's beard was gone, so was his childlike personality. Alan originally had the upper hand as his "guidance" following his divorce, but by Season 10, Walden is clearly the more mature one in the house, often acting as Alan's conscience to show how far his personality has gone.
Chick Magnet: Seriously. Every girl on the show who has met him expressed attraction towards him in some way.
Nice Guy: He's a genuinely good guy who, despite being a little sharp-tongued to Alan, is kind to those around him and rarely ever antagonizes anyone (again, unlike Alan, whose behavior he actually has a reason to scoff at). And, unlike Alan, he actually feels remorse for his actions and realizes when he's made a mistake.
Vitriolic Best Buds: In Season 9, he was fairly sympathetic and generous to Alan, but in Season 10, he seems to have discovered most of Alan's gnomish qualities and threatens to kick him out of the house multiple times. Regardless, he and Alan know that whatever happens, they can count on each other.
The Alcoholic: Naturally, like Charlie, her drinking habits have been toned up in recent episodes.
Compressed Vice: Portrayed as an out-of-control alcoholic in ""Not in My Mouth!", with no previous indications of a drinking problem. Her alcohol issues appeared inconsequentially in the following episodes.
Relationship Revolving Door: Dated Alan consistently in season 8 until she left him for her ex-husband, then they got together again briefly and broke up due to Alan's paranoia that she was sleeping with Charlie. They got back together in Season 9 because she can fart like crazy and he won't leave her. They were engaged in Season 10 and then they broke up, seemingly for good. However, in the second episode of Season 11 she began sleeping with Alan again, but they are not in a relationship, as she has a boyfriend, Larry. Alan eventually wanted to restart their relationship and planned on proposing to her, but Larry did it before he could. After that, Lyndsey stopped sleeping with Alan. Later, she tried to restart the affair, but by then, Alan was dating Larry's sister, so he rejected Lyndsey.
Butt Monkey: Offscreen, his life may be just as bad as Alan's: He was only a substitute for Charlie when he was dating Rose, and mentioned in an episode that he got a decent job as well as a wife within a 2-year radius, only for all of that to leave him. He's also envious of Charlie's lifestyle and easygoing demeanor, calling him a "genius."
Crazy Jealous Guy: To the point where he hires a private investigator (who turns out to be Rose) to get the scoop on the guy Lyndsey's been cheating on him with (unaware that it's his new best friend, "Jeff"). He thinks it's Walden, though.
The Ditz: He was completely oblivious to many of the slip-ups Alan made about sleeping with Lyndsey.
Flanderization: And in less than ten episodes, too. He started off as being simply too naïve to pick up on the fact that Alan and Lyndsey were cheating behind his back; then, he's suddenly a full-fledged Ditz who isn't bright in the least.