Character Development: He becomes less shy in the Disney series and gets more of a backbone as the series goes on.
Charlie Brown Baldness: Made odder by the fact that he needed to get a haircut in one episode, and in another episode, worried that he was going bald. However, most fanart and the live stage show made him a brunette.
Clear My Name: Doug's had a few incidents where he's been framed for something he didn't do and tried to figure out how to fix it. A lot of times, though, something else went and fixed it for him.
Clear Their Name: "Doug's Christmas Carol" and trying to save Porkchop from being put down.
Ridiculously Average Guy: He's not really Book Dumb, but also not a straight-A student, he's not very handsome, but not ugly (he's cute, though), he's not much of an athlete, but not terrible in athletics. He even described himself as being "painfully average".
It culminates in the second-to-last season where finds out that his permanent record just says "average" in all the fields.
He does have some areas where he excels though, like the arts (it must run in the family), as he's shown to be skilled in writing, drawing, and music.
Vocal Evolution: In the "Doug Can't Dance" pilot, his voice was more high-pitched and nasal compared to his voice in every other episodes of the Nick series. Then during season four of the Nick series, his voice started to get lower.
Book Dumb: Subverted. While Skeeter often downplays his intelligence in the Nickelodeon version ("But I'm bad in math! I could be wrong!"), the Disney version reveals that he's actually one of the best students in his class, only earning his first ever F after creating a robot that did literally everything except what it was assigned to do.
An episode of the Nickelodeon series has him eligible to attend college, and Doug has to deal with the possibility of losing his best friend.
Homeschooled Kid: In the first episode of the Disney version, she tells Doug that she's only going to be in middle school for a couple of hours in the afternoon and would be home-schooled with her dad. Eventually ends up back in public school full-time after her dad gets a teaching position.
Catchphrase: Joeycookamonga! At least this was it in the Disney version, although, he DID say it in "Doug's in the Money" for the first time and only time in the Nick series. Another one that came up more often was "Sayonara, suckers!"
Daddy Didn't Show: Roger wanted his father to come to a wheelbarrow race, but his Dad never bothered to show up.
Disappeared Dad: His parents are divorced. The father supposedly lives in nearby Bloatsburg but never comes to visit (and Mr. Klotz moved out when Roger was just a baby.)
Even Evil Has Standards: Roger may be a bully but he often uses verbal rather than physical since any form of the latter is taking it too far, even for him unless he's the one doing it obviously. Same goes if it's a threat.
He's forced to think about this when he issued a fight but only to back down after getting freaked about Doug's tactics, which didn't involved a single hit.
Freudian Excuse: He sabotages a Father/Son picnic because his own father refused to show up (and it's implied that wasn't an isolated incident).
Hidden Depths: In "Doug Wears Tights," Roger demonstrates some surprisingly good dance skills. He actually played the Rat King in the town's amateur production of The Nutcracker. Between his dance skills, his painting ability (which was illustrated in the Disney series), and his guitar playing one could say that Roger is a bit of a renaissance man.
Meaningful Name: The acronym DINK stands for "Double Income, No Kids" which quite accurately describes the Dinks.
Nice Guy: Mr. Dink, to the point where he's actually moved to tears when he learns that Doug and Skeeter have been working to replace the grill they accidentally broke -he's just so touched that they would do that for him.
She Cleans Up Nicely: Went away one summer and came back slimmed down, more 'developed' and with a slightly different hairstyle.
The Ace: Deconstructed twice: The first time it's shown the kind of pressure he's under to live up to the example set by his brother who's Always Someone Better, the second time it's shown that for all his skills he's a really lousy artist.
Lovable Jock: Unless he lets his competitiveness get the better of him, he's really nice.
Al and Moo Sleech
Amazingly Embarrassing Parents: Played with. A lot of the kids think their dad's some sort of insane and amoral Mad Scientist that Al and Moo hardly try to deny, and in fact act afraid about any of the kids meeting him. However, when we meet the man he's... a donut maker. Granted he builds his own equipment, but hardly the sort who conducts 'strange experimentations.'
Even Evil Has Standards: Lamar Bone has made himself known, especially towards Doug and company, he's the one person that often enforced the rules on them if denied a chance to explain but he can be overruled by anyone at a higher position than him and one person has that power... Principal Buttsavitch.
He also won't put up with students being in fights, that includes Percy Femur... yes, family members are fair game.
Just the Movie? What about the episode where his company was marketing Nic-Nacs to children with his knowledge? Or the episode where he tried to kill a dog for saving his kid from falling through the ice (on Christmas)? He definitely is the Big Bad of the the show and arguably the Biggest Jerk.
According to the Disney Wiki, Bluff has also done many illegal things such as rig a contest, get government agents to go inside a house without a search warrant, torture, and bribe authorities.
One Judge to Rule Them All: In Doug's New School. After Principal (formerly Mayor) White holds a contest to name said new school, Mr. Bluff names it the "Beebe Bluff Middle School" after his daughter, making the whole contest (and conflict of the episode) pointless.
Papa Wolf: Very protective of his beloved daughter Beebe. When it seems that Porkchop has attacked her in Doug's Christmas Story (when he was really trying to save her from thin ice), Mr. Bluff's actions border on Knight Templar Parent. He strong arms then-mayor White into forcibly incarcerating Porkchop in the county's toughest, meanest dog pound, starts a public smear campaign against Doug and his family simply because they protested Porkchop's harsh treatment, and blatantly attempted to rig Porkchop's trial by overdramatizing Beebe's injury. (the leg cast was clearly fake)
Rich in Dollars, Poor in Sense: In one episode, he tries to "inspire" Doug with the story of how he started his bumper sticker business all by himself... before he remembered he was filthy rich and hired people to do all the hard work for him.
The Mentor: Essentially is this to Doug when Guy sends him out to do an investigative report for the school newspaper. A Running Gag throughout the episode was her advice being proven wrong mere seconds after she gives it to him.
No Hugging, No Kissing: Guy and Sally work together, but yet as much time they spend with each other, there's absolutely no romance between them.
Plot Allergy: In one of the "Doug" books, we find out Sally's allergic to chalk. Due to the fact, Doug is trying to find out who drew on the wall with chalk.