While a lot of this level's visual design comes from Super Mario All-Stars, the use of statues shooting lasers from their eyes, in place of lava pits, came from a much earlier game design I'd made as a child.
The wireframe blocks phase in and out of existence, in synch with other such blocks that, in the picture, are currently phased out.
The use of a cannon in place of Bowser derives from an old Classic Mac clone of Super Mario Bros. called 'Amazing Dudes. In this game, it shoots fire across multiple screens that must be used to burn the thorns (if you don't have the firewheel powerup).
The teardrop is another powerup that makes you immune to fire damage as long as you carry it, intended for use throughout hypothetical later levels as well as the boss.
Screenshot of a very unfinished 2-1: