They turned vampire slaying badass Simon Belmont into this:
He's every narcissistic douchebag cliche you can imagine. Not to mention they made him a wimp as well.
Poor old Mega Man got turned into this green armoured, visor wearing midget who's voice sounds like a chronic smoker.
He also had this annoying Smurf inspired tic where he said "Mega-[noun/verb/additive]" in his dialog.
You wouldn't know at first glance, but that's supposed to be Roll in this shot.
Pit was also turned into this ugly little cherub.
Like Mega Man. He too had an annoying tic by saying "[noun/verb/additive]-icus" at the end of every sentences.
He even suffered from the same problem as Frankenstein's Monster, where he was called "Kid Icarus" throughout the whole show.
That alone proves the writers never played the games.
Mother Brain was the main villainess of the series. She looked as in-name-only as Simon did. (Booger-face & brain in a jar)
The only saving grace of this version was the fact the late Levi Stubbs voiced her in the same tone and mannerisms as Audrey II.
When the second season came out, they introduced a new character to promote the Game Boy...
...With an anthropomorphic Game Boy who was the Cousin Oliver of the series as he was just a blatant marketing gimmick.
Out of all voice actors they chose for him, considering the rest of the cast was Canadian. He was voiced by Frank Welker!
Using the same voice he used for Jinx the robot from the forgotten 1986 movie Space Camp.
Yes, even Donkey Kong was in the show. But he was turned into nothing but another generic King Kong clone.
He was just an obstacle for both the heroes and villains, that wanted to be left alone.