If there's one thing people complain about more than the wonky storylines of Captain N, it's how radically changed a lot of things are. Considering it's a cartoon that, at the end of the day, is just meant to entertain viewers and get them to buy officially licensed Nintendo products, whatever makes a passable cartoon is what I presume to be the producers' top priority.
Whether it's for legal reasons or simply to make it easier to convert into a cartoon, a ton of things were tampered with, and personally I believe it's what makes it more interesting. If it were as game-accurate as possible, it'd just be Kevin, Lana and Duke going about with a bunch of silent protagonists, and that'd be no good. And Simon's main drawback would be being thrown back four feet by colliding with a bat.
BO JACKSON BASEBALL
Bo Jackson is really about the only true carryover from the game, aside from the whole baseball thing. I don't think sports games are cool enough yet to make them about celebrities running around and killing evil equipment.
Simon Belmont's appearance has changed considerably over the years, and even he has fallen victim to the pretty boy treatment of all other Castlevania protagonists, but one thing he's never been is a pilot. Captain N takes some extensive liberties with how he looks, but he's still got the whip, the axes and the maces and all kinds of fancy doodads lying in his backpack. He also shares the same bodily structure as Launchpad from Duck Tales.
Trevor Belmont suffered (depending on your opinion) the same fate, but it's no big whoop. I'll take a flight jacket over a chainmail skirt any day.
The Count, or Dracula as he should be known, appeared in the previous seasons of Captain N in yellow, apparently, but I can't confirm because I haven't seen them; here he's in a much more fitting blue. For game accuracy it's rather questionable, but for public domain accuracy then it's more or less spot on, maintaining the wacky accent and all.
I've no idea what his little orange companion is based off, though. If anything.
The Count's son, Alucard, was changed into a skateboarding radio-listening sunglasses-wearing no-good punk, who uses enough slang to rival the Teenage Mutant Ninja Turtles. He does shoot fireballs from his cape, but that's as close to the game it gets.
The Poltergeist King, believe it or not, is from the games, but makes no appearance in them. He's mentioned in the manual of Castlevania 3. Direct extract!
You [Trevor Belmont] must also possess the strength to wield the mighty Battle Axe and Mystic Whip, which were given to you by the Poltergeist King.
From what little information there is, he's about accurate, swiping the weapons off the wall when he vanishes in his sole appearance. What fan would ever remember this guy? Nobody. Bless the lord for cartoon writers.
Astos is just your generic armoured demon in the cartoon, but in the games he's a naked, hairy elf monster person thing who disguises himself as someone else. However, his scheme of robbing stores and such like in the cartoon is vaguely reminiscent of the pirates who invade a city, but don't actually do much looting. Hence vaguely.
Although unnamed, I assume the witch is Matoya. Matoya looks nothing like the Wicked Witch of the West and has rad theme music, but she does have a few talking broomsticks.
The prince of Elfland, in the game, is sent into an eternal sleep by Astos and needs awakened, which is more or less the same as the game.
JORDAN VS. BIRD: ONE ON ONE
Larry Bird's hair doesn't look much like the real deal. And Michael Jordan doesn't make an appearance.
Although not from the game, here's Hoopless and Urkel.
The title of the game is merely a nickname for the character, apparently, as he's really called Pit. The cartoon calls him the game name. Aside from the colours and simplification of his design, cartoon Pit is more or less accurate; he's ginger instead of brunette, has gloves instead of bracelets, lacks sandals and ankle bracelets, and his tunic is a mild yellow rather than white (though the manual makes it a wide range of colours so no big whoop).
Eggplant Wizard resembles an eggplant more than his game counterpart, his lips grimy and yucky while they're pretty smooth in the artwork. His only clothing is a cape, while the game version wears a robe as well.
Mega Man went from his traditional blue and cyan colour scheme to a rather ugly green, yellow and turquoise one. The yellow appears to have come from the boxart of the first Mega Man, with the visor coming from his appearance on the box of Mega Man 2, but aside from being a robot I've got no logical explanation for his croaking voice.
Aside from being made really ugly, Rush is more or less accurate, ignoring the lack of light tones and artistic license taken to give him a face only a mother could love.
Dr. Light's coat is green and he looks fit to be on a box of Rice Krispies.
Dr. Wily is pretty accurate, though he's got one of those German accents when in the games he's just meant to be American, apparently. And his hair looks like Mr. Messy.
Doc Robot mimics the Robot Masters from Mega Man 2 in the games and looks nothing like a doctor of medicine or science, but the cartoon takes the name literally and makes him a robot clone of Wily.
Top Man added some turquoise to his palette, thus ruining a perfectly good colour scheme.
The peace keeping robot is likely to be based off Gamma from Mega Man 3, but I severely doubt the designers had any source material aside from the manual. They did at least know it was hijacked by Wily.
That says it, doesn't it?
MIKE TYSON'S PUNCH-OUT!!
King Hippo is just a regular fat guy in the game, his caricature style appearance being the only real abnormality about him. The cartoon, however, makes him blue and gets him saggy breasts with nipples, which really kind of gross me out. He doesn't have a bandage on his belly button, though.
Mike Tyson makes no celebrity appearance, sadly. =(
ROBIN HOOD: PRINCE OF THIEVES
Based off the 1991 film of the same name, Robin Hood doesn't look much like Kevin Costner.
Cartoon Tetris has a story.