...Which reminds me, I think I'll sling up the rest of my own glitchy NES codes.
BART VS. THE WORLD
AEIOUX - Sometimes funny music.
SUPER MARIO BROS.
ZOPOIK - Raised ground and stranded enemies.
XPAAIV - Scorched Mario on Fireflower.
SKZUNO - Flattened Goombas, Shellcreepers are weeds. (Or it could be SKZVNO, with my writing then.)
GVXOEO - Tunnels in pipes and levels uncompletable.
OPUNY - High jumping and slow floating Mario.
NYVTYV - Hitting coinboxes crashes the game.
SONETX - Play from demo screen.
YSAOPE + YEAOZA + .....
KEAPYA - Start on World 9.
NEAPYA - World 10.
VEAPYA - World 11.
EEAPYA - World 12.
EPOZXU - World 0.
SIPPNG- Waterworld.
YULENS - No freebies.
POEISA - Invincible, with the dead enemies dishing powerups!
SSPPYK - Extra difficulty.
SAGOZK - No backgrounds.
SZLIVO - Enemies can't hurt you.
SSASSA - Always Starman.
PINAAO - Play game in pause mode.
NNAIKE - Powerups KILL.
IONATX - SS helmets instead of Goombas.
OPASSE - 1-Ups now powerups.
AXEAXP - Art school deco.
NOKEAG - Powerups double as 1-Ups and other novelties.
PZZONO - Go down any pipe.
GGOPAK - Nuclear waste Mushroom Kingdom.
KIPAXI - Castles redecorated.
APZIGU or OXZLLU - Fire even when little Mario.
POZIGU - Falling fauna.
Level 1 only:
VIPPOS - Hammer Bros., moving platforms, jellyfish and others.
SIPPOS - Flying fish and lifts.
GIPPOS - No enemies.
KIPPOS - Fewer regular enemies with lifts, jellyfish and flying turtles instead.
XIPPOS - Fireballs and Bowser. But level freezes.
EIPPOS - Twirly fire, Hammer Bros. and a tougher level end.
SUPER MARIO BROS. 2
EESEGL - Music runs slow.
PESEGL - Fast for a bit.
SESEGL - Gramophone winding fast then down.
VESEGL - What the hell.....?
Also use with LELALU for extra effects.
EAXAPGGA - Jet Dress Princess.
EESEGLGA - Jet Fart Mario.
EAEEZGPA - Luigi jumps extra, extra high.
PIXAOIAA - Princess takes extremely long time to land.
ISOPKE - Bits of floor missing.
NANANA - Goes spotty.
NULUNU - No enemies.
LULOLU - Some parts trickier.
AEEPUZAG + IUEPSZAA + TEEPVZPA - World One.
PEEPUZAK + IUEPSZAA + TEEPVZPA - Negative World. (May stall.)
XEEPUZAG + IUEPSZAA + TEEPVZPA - Desert-Grasslands mix.
VEEPUZAG or UEEPUZAG + IUEPSZAA + TEEPVZPA - Mushroom Kingdom still a building site.
NEEPUZAG + IUEPSZAA + TEEPVZPA - Trapped in Luigicage.
SUPER MARIO BROS. 3:
VOPZPE - Crazy rompler.
KUNTYS - Rompler on map.
KUNTYL - No sound on map.
SSOSSZPA + VTTTTT - One less sound channel.
SSUZVUEE - Car-speed fast run.
GOPZPV - Swims through the air.
GOPZPE - Aircraft sounds on flight.
IOPZPU - Mario breaks wind when becoming Super.
YEUZUGAE - World Zero.
GAPPOK - Logie-Baird scanlines Mario.
OEPZXZ - Opening screen turtles radioactive.
IOPZPV - Skating Mario in Battle Mode.
AOPZPE - Fire alarm Mario.
NUKIES - Disorder.
GAZZAP - Changes map screen.
VIZGXE - Cowardly enemies.
VIZGXL - All boxes except prizes turn to jump blocks, woodblocks to white slabs and plenty more besides.
YOILEN - Slow Mario.
OOPZPY - Plants disappear.
TOILET - No enemies.
VIZGXY - Starman by David Bowie.
SOKKIT - 'Friday Afternoon' buggy version.
KOKKIS - Olde-Worlde Mushroom Kingdom.
TOILEG - Level doesn't finish.
GIZGXL - Emptier Mushroom Kingdom.
AIZGXL - Turtles die when stomped.
AEIOUL - Littered screen for harder game.
OOPZPU - Slippy Mario in Battle Mode.
OXKXGLIA + XXKXGLIA - Totally invinsible, though can only change to various Super Marios on map
screen for Toad's House and can't use pipes.
EAZULX - Enemies disappear behind scenery.
YAZULX - Most enemies absent.
APZLTG - Hammer Bros. indecisive.
APZLTS - Muddled levels for more challenge.
EEUXKGAA - Start as Super Blob Mario.
KEUXKGAA - Half frog, half Tanooki.
NEUXKGAA - Scrambled Mario.
VEUXKGAA - Plastic Surgery Leftovers Mario.
KEUXKGAA - Warhol Mario.
YEUXKGAA - Unlimited level skip on map screen and Plant Mario on levels.
XXKXGLIA - Concrete Mario. Can't use pipes.
AOZXXL - Negative World.
OEPZXZ - ALL activities a 1-Up.
OOPZPE - Drunk code.
GOPZPV + SZUAUNSO + YEUXKGAA - Mario swims in the air but doesn't look a plant.
NIGGAS - Enemies faint as if Mario really stinks!
I think I'm going dyslexic spellchecking that lot.