Animation Bump: The animation for the Theme Tune (see below) was done by a different studionote Canvas Inc., who also did the title sequence for ProStars than the episodes proper, and it uses a clear, smooth, professional style. The animation for the rest of the show was anything but clear, smooth and professional, with errors that don't even need frame-by-frame analysis to spot.
Cut Lex Luthor a Check: Koopa actually seemed to have a profitable, legit business going in "King Scoopa Koopa". Even the Mario Bros. were impressed. Of course, Koopa just had to go turn everyone into chickadactyls For the Evulz.
Gasshole: Yoshi also burps several other times in the series, mostly after eating.
Getting Crap Past the Radar: Also at the end of "Gopher Bash", Luigi punishes Yoshi for eating all the food, telling him, "Since you ate the whole thing, now you can do the hoe thing!" Although he obviously means "hoe" as in the gardening utensil, it's pretty easy for one to joke about what it sounds like.
Leitmotif: Since the show re-arranges most of the music from the first two Mario games, the tunes are indicative of the character or type of environment that is currently on-screen. Examples: The Valley of Bowser theme playing when Koopa's castle is shown.
Limited Animation: Sometimes it gets to the point where you can't tell if what's happening is intentional or not.
Mutagenic Food: Eating enough Chickadactyl Eggs will turn the consumer into one themselves
My Name Is Not Durwood: "That's WIZARDHEIMER!!!" note Among the various name screwups: Wizenheimer, Wizardwhatever, Wiseacre, Wisecracker, Wizenwhatchamacallit, and Wisenwhatever.
Off Model: The animation quality of the show was rock bottom to begin with, but was brought down ever further by outrageous animation errors that frequently pop up in the shorts, some of which are so blatant that you don't even need to freeze frame the cartoon to notice them. And Mario and Luigi still have the colors of their overalls and shirts swapped in this cartoon. King Koopa still remains off model in terms of coloring.
Happens in "Send In the Clowns", where Mario and the cavemen don't realize the clowns in King Koopa's circus are actually Rexes until one of their noses falls off.
Also happens in "Rock TV" when Koopa is in a paper thin disguise promoting the titular product. No one can tell it's him even though several of the shows he mentions even have the name Koopa in the title.
Pragmatic Adaptation: While not for the whole series, the episode "Send In the Clowns" explains why someone as mean and nasty as King Koopa would have a helicopter with a clown.