Cats Are Mean: Inverted. Everything is trying to kill the poor cat. And I mean EVERYTHING.
Death by Genre Savviness: The player, assuming that he/she is familiar with the general gameplay of Super Mario Bros. 1, will die over and over again precisely because the entire game is devoted to subverting that Genre Savviness and killing you. For example, that pipe that should lead to a secret area? Kills you. That star that should make you invincible? Kills you. That invisible block that should contain a 1-up mushroom? Contains poison mushrooms and kills you.
The Dev Team Thinks of Everything: Nearly every possible route through the levels was foreseen by the developers, and then all but one of those routes were all filled with unavoidable death traps to limit the player to using only a single precise route. For example, in the fourth level, there's a place where you needs to jump over a lava pit. Jump too close to the ledge? You hit an invisible block. Try to jump onto that invisible block and then jump over the lava pit? The invisible cloud kills you.
Didn't See That Coming: Many traps are well-hidden and come out of nowhere, such as jumping off a ledge, hitting an invisible block, and falling to your death.
Emoticon: Syobon, Buun, and Kuma are in fact 2ch emoticons given life. See Memetic Mutation entry below.
Meaningless Lives: Played literally. If you die on your last life, your counter just goes negative and acts as a death counter from there on out.
Mega Neko: The cat may be one of these - he's the same size as Mario would be.
Memetic Mutation: Syobon no Action characters are in fact, 2ch ASCII characters/emojis. Syobon itself is the onomatopoeia of a character making a disappointed, catlike face (think Japanese equivalent of "okay.jpg" meme). Other characters, including the white Pedobear lookalike (which is just called "Kuma" in Japan), to floating Buun (onomatopoeia of a person spreading his/her arms and running, precisely the pose the enemy takes while floating) are also 2ch characters. Lines said by enemies or Syobon-kun when killing/getting killed are also memes, such as when random enemies shout Mudamudamuda!!
Red Herring: The Bowser Expy and poison mushroom at the end of the last level. Either one kills you, but eventually you'll figure out that you're supposed to use the mushroom to kill "Bowser" instead... but, if you do so, all that does is lead you straight into one last unavoidable Kaizo Trap in the form of a giant chicken man standing in for Toad. To beat the game, forget about "Bowser" and the poison mushroom and instead let the throwing enemy carry you above the level, allowing you to bypass "Bowser" and "Toad" and find the real ending.
Rule of Funny: Your life counter before you start playing starts at x2 lives... and after losing your "last life," it will go infinitely into negative numbers. Many players die hundreds of times.
Shout-Out: The game is a parody of the old Super Mario Bros. games.