ToeJam & Earl

The entrance to Floor 0 is found on Floor 1 but you can't get to it from the start. You can wait until you find Icarus Wings, a Jetski or an Inner Tube randomly, or you buy a pair of Icarus Wings in Floor 3's mailbox (bottom present if you've not discovered them yet). Save first then buy the item and drop down to Floor 1 by falling off the edges. On Floor 1 use the Icarus Wings and head to the south west of the map over the water until you reach a small island. This island will have a hole in the middle of it you can drop down into which leads to Floor 0.

Down here is a hot tub that you need to jump in and the trophy will pop. Also if you get a lemonade from the stand you will get an extra life. If you want you can then reload your old file saving your bucks, or fall off the edge to be taken back to the highest floor you've reached so far.