Cuckoo Condor is the boss of the Ruby Passage in Wario Land 4. Although her true form is revealed rather quickly, her initial form is an extremely grotesque mechanical monstrosity that vaguely resembles an old-fashioned cuckoo clock.
Prior to her clock suit being broken off by Wario, Cuckoo Condor attacks using a grabbing claw that can also ironically be used against her by shoulder-ramming it so that it swings straight up and hits the living weather vane atop her head. She can also launch buzzsaws and electricity balls at Wario using her suit's mechanical arms, but rarely gets the chance to do so (and even when she does, said attacks are very easy to avoid).
After taking enough damage, Cuckoo Condor's clock suit indeed breaks off, revealing an ever-so-slightly less deformed vulture-like creature that floats around and lays eggs that hatch into exploding chicks. Wario then defeats Cuckoo Condor by catching said eggs and throwing them at the aforementioned weather vane atop (not to mention permanently attached to) her head. Once Wario has finally killed(?) her, Cuckoo Condor explodes in a cloud of smoke, much like the other bosses (not counting the Golden Diva's lips being knocked off of the screen during her final phase).
- Unlike Spoiled Rotten (which looks harmless during its first phase but looks horrifying during its second phase) and the Golden Diva (who is already very creepy-looking during her first and second phases but looks especially scary during her third phase), Cuckoo Condor looks like a living embodiment of a nightmare during her first phase but looks relatively harmless (albeit still rather odd to say the least) during her second phase. Like the Golden Diva but unlike Spoiled Rotten, Cuckoo Condor also is ironically much easier to deal with during her scary-looking phase.
- Despite the Ruby Passage itself often being quite difficult by the game's standards, Cuckoo Condor is actually the overall-easiest boss in Wario Land 4 by incredibly far, due to her Super Hard Mode version barely even being challenging to beat quickly enough to get all three of the treasure chests from (while Aerodent's and Catbat's Super Hard Mode versions both almost require players to use "damage-dealing assistance" items in order to get all of their treasure chests, and Spoiled Rotten's Super Hard Mode version almost requires players to use said items just to be able to beat it at all due to the infamous 15-second time limit that it features; while not nearly as difficult as Catbat's and Aerodent's, Cractus' and the Golden Diva's Super Hard Mode versions also leave very little room for error if players are planning to get all of their treasure chests without using said items).
- Wario is able to "pass through" Cuckoo Condor's first form in ways that clearly shouldn't be possible.
- Cuckoo Condor might be a parody (of sorts) of the Chozo race from the Metroid series, or at least a parodic foreshadowing of the Chozo Ghosts that would later appear in Metroid Prime (roughly one year later); considering how much the Wario Land series has in common with the 2D Metroid games, this wouldn't be terribly surprising.