Grass
grass adds 8 pixels to the top
Byte code
planet blupi includes a serializable scripting language to control all the entities. this makes it very easy to add new entity behaviors to the source code. and since the script is represented as bytes, scripts could be included with levels (if the developers ever implemented it)
planet blupi's bytecode has functions for creating, removing, and detecting blocks. if it was actually included with level data, it would be possible to make logic gates, leading to some crazy stuff.
Treasure
Treasure chest does not contain coins, but golden eggs.
Animation bug
the animation counter for objects only goes up to about 32000. it only takes about a half hour for them to reach that and overflow to negative they fixed it for the sequel (mostly)