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The Kaeru Block appears in the Game Boy Advance game Wario Land 4. These blocks have frog faces on them. Similar to Dotted-Line Blocks and P Blocks, they can either appear solid (Wario is not able to walk through them, but can walk on them), or transparent (Wario is able to walk through them, but not on them). Depending on whether Wario has hit the switch, the blocks will change their appearances (e.g. all transparent blocks will become solid, and all solid blocks will become transparent). Some new areas are only accessible by hitting the switch, so the player may have to find the rest of the jewel pieces or maybe even Keyzer within the time limit.
In the level Hotel Horror, a few of the red doors have a Kaeru Block sign. These kinds of doors will only unlock once the level's switch has been hit. The level Domino Row contains a unique type of Kaeru Block. Only the top half of the block is filled in, and Wario is able to move upwards through the block, while still using it as a place to stand.
In Wario Land: Shake It!, shake blocks are functionally identical to Kaeru Blocks except their opposite reactions come in two colors. Furthermore, they react to the unused switch returning from Wario Land 4. The internal name of the shake blocks indicates that they were originally going to be the frog design returning from Wario Land 4. Additionally, the word kaeru may be a pun, as it translates to "frog" as well as "to return", which is when the blocks activate.