There is an unused graphic of a grasshopper saved in the game's memory. According to the developers, it was to serve the same role as the Spider does in the final game.
Contributed by MeleeWaluigi
In the Intellivision port are 2 hidden messages in the ROM.
The first one is:
"Why are you diassembling this code? That isn`t nice!"

And the second one is a joke:
"Joe: Knock knock!
Moe: Who`s there?
Joe: Santa!
Moe: Santa who!
Joe: Santapede is comin` to town!"
Contributed by DeerBoarDude