Buckwheat comes off as an Ethnic Scrappy to modern viewers, but having a black character accepted as an equal by his white peers was still a huge step forward then.
Stymie is easier to accept; he may be poor and illiterate, but he is easily the smartest Rascal of the gang before Spanky took over that role.
Follow the Leader: The shorts spawned a few imitators, such as Mickey McGuire, Hey Fellas, and McDougall Alley Kids.
Harsher in Hindsight: In "Fish Hooky", the kids decide to write phoney sick notes to their teacher in order to play hooky. Stymie suggests saying he has Pneumonia on his. Matthew Beard (the actor who played Stymie) died of pneumonia in 1981.
Real Song Theme Tune: For a brief period, the series' theme music was Ray Henderson's "That Old Gang of Mine..."
Some modern viewers are put off by Darla's wriggling and vamping, especially in the musical numbers.
Petey is a Pit Bull breed (sources differ on whether he is a Staffordshire Terrier or an American Pit Bull Terrier). Modern Dog Stereotypes have them as dangerous and often guard dogs. In the early 20th century, they were seen in a similar way to German Shepherds are today—protective of family, sweet tempered, and great with kids. Petey even helped boost their reputation as "nanny dogs".
A lot of the humor surrounding black characters tends to be of the old-timey Uncle Tomfoolery variety in which much wouldn't fly today. This tends to be negated a bit by the fact that Stymie was an intelligent clever kid. Also, they were just as much equals to the white kids and the latter never made an issue out of skin color.
The shorts Teacher's Pet, School's Out, and Teacher's Beau mention the Rascals' teacher getting married and them getting a new teacher. This was Truth in Television in some places even into the 1930s; female teachers were not allowed to marry. Those that did had to leave their profession. This may come off as bizarre to modern viewers.
Buckwheat is a boy, though an unrelated character with the same nickname was previously played by a girl.
Earlier; Farina followed a similar arc. He started out as Silent Era Ernie/"Sunshine Sammy's" little baby sister.
"Weird Al" Effect: The Flory Dory act from "Our Gang Follies of 1936" was a parody of a popular Edwardian musical comedy called "Floradora."
Tropes specific to Hanna-Barbera's version:
Hilarious in Hindsight: In "Pete's Big Break", Buckwheat is shown operating a makeshift movie camera while the kids rehearse for the TV commercial. His voice actor, Shavar Ross, grew up to become a respected filmmaker.
Tropes specific to the 1994 movie:
Adaptation Displacement: Bring up "The Little Rascals" to nearly anybody under 35 and they'll likely assume you're referring to this movie. Mention the original series, and you'll be met with surprised looks or head scratches.
Audience-Alienating Premise: For some fans of the original shorts, the fact that the children aren't poor and look like yuppies may stop them from seeing this version.
Alfalfa demonstrating why you should Beware the Nice Ones when he punches Butch hard enough to knock him into a muddy pig pen. Woim, intimidated by this, then throws himself into the mud so avoid getting punched.
Darla kicking Waldo out of his own car and finishing the race herself.
Waldo is an arrogant, spoiledJerk Ass, but he crosses into this territory when he uses tire spikes against Alfalfa and Spanky in the race, a potentially dangerous trick. Darla even calls him out on this, and proceeds to break things off with him and kicks Waldo out of his own racer.
Likewise, Butch and Woim cross it when they throw a smoke bomb on Spanky and Alfalfa's racer.