Bowser

Bowser is a recurring character in the Mario series. Being the primary antagonist, he coudn't be left over from SMBX. He has 2 separate styles and AIs.

Super Mario bros. 1 AI
Bowser will walk slowly forward and backwards, shooting Bowser's Fireballs and Hammers. He can be hurt from many projectiles, including fireballs, shells, hammers and bombs. After a few hits he will be defeated.

Graphics Folder number: npc-200. Flame: npc-87

Super Mario bros. 3 AI
Bowser will hop in one place while hurling Bowser's Fireballs at the player. After an amount of time, he will jump really high, stand above the player, and stomp down. The stomp can break certain castle tiles found in the SMB3 Special tab. He is immune to fireballs, and needs to take many hits to be Ko'd. However he can be dealt easily by luring him to lava pits and breaking the aforementioned tiles for falling down the hole he created himself.

Graphics Folder number: npc-86. Flame: npc-87

Trivia

 * If you place tiles directly above SMB3 AI Bowser, he might penetrate the wall and jump shortly afterwards, disappearing.
 * If you modify the hammers that SMB1 AI Bowser throws, that will effect Hammer Bros. hammers as well, since they use the hammer projectile.