The little hole in the 1-2 Secret warp to World 4 can be thwarted with Super/Fire Mario.
Steps
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1.Slide under the first brick and break it. (You need to run and crouch!)
2.After you do that,go back.
3.Make sure you go allll the way to the pipe.
4.Run and just slide under 1/2 of the brick.
5.Break it.
6.RUN OVER THE GAP!!!!
That`s how you do it!
You have to master it,though.
By the way,If you are an american and trying to get SMB2j,Here is 2 ways.
1.ILLEGAL:
1.Download VirtualNES. Then find the ROM. I would not actually do this.
2.If you have the Famicom,find a pirate,which might not last long,and might be very crappy.
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2.LEGAL
1.If you have a Wii,Get a Wii/DSi points card,go to the Wii shop channel,Find SMB:Lost Levels! (Points:500)
2.If you have a GBA/SP,Look around on eBay for a copy of the GBA version.
3.If you have a GBC,and Super Mario Bros DX,just unlock it!
4.If you have the Famicom Disk System,look around for a copy of SMB2.
You can thank me later.