Null Egg

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Individual Level Strats

World 2


World 3


World 4


World 5


World 6



  • The Null Egg was originally thought to be a random occurrence at the end of 2-2 that would cause the game to crash. That was until ArneTheGreat looked into it further and discovered that the crashes were caused by a rat carrying an egg.
  • If you grab the egg from the rat (without destroying him) and he despawns, the egg will also despawn because it is tied to the rat's sprite. When this happens, it creates an open sprite slot in your egg inventory - a null egg. This slot is subsequently filled by the next sprite that loads in, even if it's a non-egg sprite like an enemy or collectible. Since sprites being loaded into the egg inventory in this way is not supported by the game, it usually results in a crash.
  • After some experimentation, it was figured out that the boss key sprite could be obtained and then used to beat levels soon after they begin. This created the first truly broken/glitched speedrun category Magical Journey.

The following video explains how sprite ID slots work with regards to the Null Egg and also demonstrates the different uses of it.

Magical Journey
Game Crash
Null Egg Demonstration

Getting The Null Egg

This text tutorial corresponds to the video down on the left.
Destroying the enemies in this section is to make sure the correct sprite loads into the open slot in Yoshi's egg inventory.

  • Enter the final screen with 6 eggs and do not use any.
  • Grab the rat as it jumps out of it's hole and spit it into the green Shy Guy.
  • Tongue the Skull Rat and then spit it into the Piranha Plant.
  • Jump and grab the egg that the rat is carrying before it falls down. When the rat despawns, you will have the null egg.
  • Go up the hill and tongue the first rat and spit it into the second.
  • Go back down the hill and follow the rat carrying the egg to the left, up the other hill.
  • Scroll the screen up and jump to load an off-screen rat into the open slot in Yoshi's egg inventory.
  • Complete the level like normal but do not use any eggs or kill the final Piranha Plant.

Keep in mind that the game can crash upon entering the goal ring if the setup is not done properly.

Easy Setup
Faster Setup

Getting The Boss Key Sprite

  • After getting the Null Egg in 2-2, re-enter 1-8 to fight Salvo to get the boss key sprite into your egg inventory.
  • You want to end the fight with 3 eggs if you're running Magical Journey. These eggs will be used for upcoming levels.
  • You can use your remaining eggs to throw at the water spitting fish in the second room, the red switch in the room after and one for the boss.
  • Throw one egg at Salvo and then finish the fight by spitting the small slimes into him.
  • Do not tongue and catch the egg after you throw it, otherwise it will mess up the sprite ID slots and you won't be able to get the boss key.
  • Once you complete the boss fight, you will have the boss key in your egg inventory which will allow you to beat every level thereafter really quickly.

In theory, it would be faster to use the boss explosion sprite rather than the boss key sprite but the game crashes in many levels when doing this because the level gets completed before being properly loaded.

Null Egg Tutorial For All Levels
1-8 Salvo Re-fight Demonstration

Save File Corruption

This trick allows you to unlock 6-8 after beating 2-6 by corrupting your save data. The No ACE category was created as a result to differentiate it from Magical Journey. This run is only possible on the SNES, using version J1.0

2-6 Route

This route is significantly harder. Only use this route if you want to compete for top times.

  • You have to use file 3, otherwise it won't work.
  • In 2-2, you need to collect 2 Null Eggs.
  • Make sure to enter the last room with 6 eggs.
  • Grab the first Null Egg, run to the right, scroll the screen up to spawn the Little Skull Mouser, grab the first Little Mouser that's coming out of the nest and spit it into the other one. Run left until the Mouser with the egg spawns and runs away, run right until it despawns, and while you run up the hill on the left, swap your eggs twice.
  • Run down, grab a 2nd Null Egg, stop before the Mouser Nest, scroll up to spawn another Little Skull Mouser, and then finish the level.
  • In 1-8, you don't want to shoot the fish in the 2nd room.
  • In the 3rd room, shoot the platform switch with an egg. Do not shoot the pot.
  • In the boss fight, shoot one egg, and tongue it before it dies. This is important to get the Boss Explosion in your Null Egg. (It doesn't matter if you collect it afterwards or not)
  • Finish the fight by spitting slimes into Salvo.
  • You will now have a Boss Explosion in your first Null Egg, and a Boss Key in the 2nd Null Egg.
  • Continue with 2-3.
  • Only mash one button in the intro of 2-3, otherwise you will spawn a Gusty, which will replace the Boss Explosion.
  • The Boss Explosions will finish 2-3, 2-4 and 2-5 instantly.
  • After 2-5, the Boss Explosion will be replaced with the Seesaw Log from 2-5. This is good. 2-6 loads very slowly, so with the Boss Explosion you would die before the level loads.
  • Run to the right, swap one egg before the keyhole opens all the way. This will delay the Boss Key enough, that you can enter the door.
  • In the 2nd room, ground pound where the enemy is, wait until the keyhole starts opening up (NOT BEFORE), shoot your egg up, and make your way into the door.
  • In the 4th room, run right and make your way over the platforms. Shoot another egg to delay the Boss Key once again.
  • Once you are in the last room. Flutter out of the water and bonk the wall on the right to delay running right.
  • Jump up the slope until the edge, land on the first and 2nd numbered platform, fall into the water, hold right until you are in the water, and then hold left and jump until the level finishes. (This pretty much just has a 50% chance of working, because the pixel you need to get a 6-8 save corruption is very precise)
  • Once you are back on the overworld, reset the console, and if you have done it right, you can now enter 6-8 and finish the run.

3-1 Route

This route is significantly easier but loses ~40 seconds compared to the 2-6 route. It's recommended for beginners or for marathon runs, because the 3-1 Save Corruption is 100% consistent, if done right.

  • For this route you have to use File 2, instead of 3.
  • For the double Null Egg, you don't want to swap eggs. This allows us to use more eggs in 1-8.
  • Once in 1-8 again, you can shoot the fish, the switch, the pot and Salvo.
  • In the Salvo refight, DO NOT collect the egg after tonguing it.
  • During the level intros for 2-3 and 2-5 only mash one button.
  • In this route, you just want to end 2-6 normally. Run to the very right, and then scroll up, to end the level faster.
  • In 2-8, you want to throw away your first Null Egg.
  • In 3-1, only hold right and mash one button.
  • Jump up the foam, over the red coin, run up the branch.
  • Once you start falling, turn left without slowing down.
  • When you hit the wall below the 2nd branch, flutter until the level finishes.
  • Once you are back on the overworld, reset the console, and if you have done it right, you can now enter 6-8 and finish the run.

If you accidentally collect the egg during the Salvo refight:

  • For the 2-6 route it doesn't matter if you collect it or not.
  • For 3-1 it does matter. If you do collect it, all you have to do is collect the red coin right after the foam in 3-1. (Refer to the video on the right)

2-6 Save Corruption
3-1 Save Corruption (Accidental Egg Collection)
3-1 Save Corruption

Further Information

The position of the boss key sprite affects how quickly a level gets completed. Compared to having 3 eggs in front of the key:

  • Having 2 eggs loses 9 frames per level.
  • 1 egg loses 47 frames.
  • 0 eggs loses 49 frames.

The Boss Key also affects a few levels differently depending on the version. From fastest to slowest overall version it's:

  • J1.0 > J1.2 > J1.1 > U1.1 > PAL > U1.0

The Null Egg In Other Levels

3-6 Null Egg

The Null Egg can also be acquired in 3-6. A Screen Transition sprite can then replace the Null Egg to trigger a 1-1 Warp to complete the level. Unfortunately for the IL run of this level, the 1-1 Warp is slower than doing the level normally, however, the 3-6 Null Egg can be used in 100% No Restrictions to save multiple minutes.

3-6 Any% Speedrun Using The Null Egg
How The 3-6 Null Egg Can Save Time In 100%

6-4 Null Egg

The Null Egg can even acquired in 6-4! While it is harder to get than the Null Egg in 2-2, this one actually saves time in an IL run, unlike the one in 3-6, since it allows you to skip most of the room before the boss where you would normally do the Lava Skip (or take the log). A middle-ring replaces the Null Egg and upon dying and respawning, you're placed after the lava section. All you have to do after is fight Tap-Tap.

6-4 Null Egg Demonstration
6-4 Any% Speedrun Using The Null Egg

Extra Help

Head over to the DLC page to find useful tools like Lua with sprite slots and RAM watch that will help a lot to learn and better understand specific Null Egg things.