Little Fiery Mario
Internal to the game, Mario's powerup state is recorded in two independent variables; one describes size (0=regular; 1=super) and the other tracks the 'upgrade state' (0=need mushroom; 1=need flower; 2=has flower). The 'size' decides the sprite (small on 0; big on 1) used for Mario; the 'upgrade state' decides what powerup will come out of a block (mushroom on 0; flower on 1 or 2) and what will happen when Mario is hit (die on 0; switch 'size' and clear 'upgrade state' on 1).
These states can be knocked out of synchronization. The game checks for all sprite collisions, knocks the 'upgrade state' to 0 if it hits, and switches size only when all checks are done. If Mario's sprite strikes the King Koopa sprite and the bridge release sprite in one frame, the game will register the collision between Mario and Koopa, knock the 'upgrade state' to 0, register the collision between Mario and the bridge release, and jump into the level complete loop that causes Mario to walk to the right -- and never switches the 'size' variable.
If Mario was naturally large (state 1 or 2, size 1) when he hit the switch he will stay large (state 0, size 1). If he strikes an enemy he will die (because his 'upgrade state' is 0), but he can break blocks. If he gets a mushroom, he will shrink and be unable to hit blocks; if he is hit now, he will grow again. If he gets a fire flower, his pallette will be changed and he will be able to shoot (but the game will use the large image for shooting; it will, however, keep Mario's small feet if Mario is moving.) Mario will now be Little Fiery Mario.
If Mario was naturally small (state 0, size 0) when he hit the switch he will appear to die but the level will still be beat and he will not lose a life. If Mario was unnaturally small (state 1 or 2, size 0) when he hit the switch (that is, if he does this trick twice), he will revert to his normal form. When Mario dies his size is set small and his state is set unupgraded, no matter how he died or what his state was before.
Using the third part only of a 3-code Game Genie code for "Always Stay Big" will produce similar results (the code is SZLIVO). As long as Mario has gained a power-up, he will become small when hit, then grow when hit a second time. This is a much simpler way to view the "Little Fiery Mario" quirk.
This glitch, originally discovered by gamers Grady Haynes and Tom Shoemake [citation needed], appears to have been fixed in the Super Mario All-Stars version, though you can still see it with a cheating device.
Alternate method to the 4-2 warp zone
On level 4-2 (an underground level), an above ground coin area and warp zone is reachable via an ivy vine/beanstalk. However, a variation of the 1-2 trick to get to world -1 may be used to reach the coin area in an alternate manner. Before the area where the vine is accessed is a long corridor with a lower corridor at the beginning of it. From this lower corridor Mario may be made to slide through the lower bricks in a manner similar to the -1 trick. (During the crouch-jump Mario's head must pass through the "?" block to the left of the opening to the upper corridor). After the slide, as in the -1 trick, Mario will be at the right side of the screen, ahead of usual play triggers. An experienced player with knowledge of the level can then manuever Mario (without dying or backtracking) to the coin-area pipe beyond the vine area. If Mario enters the pipe here, instead of being transported to the normal coin area, he will find himself in the above-ground coin/warp area.
This trick can also be done by accessing the vine, scrolling it halfway off the left-hand side of the screen (using the block it grew from as a guide), getting on the vine, and pressing left. This will cause Mario to switch to the extreme right-hand side of the screen, where the earlier method takes over.
Power-up double jump
When presented with either a Super Mushroom or Fire Flower, if you ensure that you are not holding A when you collect it, you can press and hold A during the powerup animation, which will result in Mario jumping from that point in midair as if he were standing on solid ground.
Wall jump
When Mario hits the edge of a wall at a 16-pixel tile boundary, he will act like he is standing on solid ground for a frame. If you can manage to press A on that frame, Mario will appear to jump from the side of the wall.
"Hat stomp"
Mario does not necessarily need to be coming down on an enemy from above to stomp it. As long as Mario is moving downward, he can stomp enemies.