The Cabinet of Failed Inventions appeared in Edd's Basement in the episode "3 Squares and an Ed."Eddy "stumbled into it" while observing the basement. Like its name suggests, the cabinet contains a number of Edd's failed inventions. The purpose of the cabinet, as Edd put it, is to remind them of their misguided attempts and to learn from past mistakes.
Starting from the bottommost shelf and proceeding upward, it contains:
1st Shelf: Volcano Vacuum (only seen in the cabinet in this episode), a jar of goop (only seen in the cabinet in this episode), an invention involving a radio