Wally is a red headed, blue feathered bird of unknown species who wears a cuckoo clock that hides most of his body save for his legs, wings, and head. His legs are disguised as a pendulum before the battle with him begins. He has red and blue feathers and an orange beak and feet. Inside the cuckoo house resides his son.
Judging by his aggressive appearance and his son's death screen line, Wally acts as the brawn of his family. He also appears to be a protective father to his son, having a cuckoo house for him to be kept safe in while Wally deals with his own enemies. Wally is even determined enough to fight until the end, no matter what happens to him in the process, as evident by the fact that he continues the battle featherless and on a stretcher.
Wally's son is the brains of his family, according to his death screen line. To defend his smart behavior, he is shown to carry around a ray gun, despite his young age. He also seems to depend on his father when he is in a sticky situation, proven when he starts crying for his father to deal with Cuphead and Mugman at the end of his phase.
"I own the air -- I fly where eagles dare!"
—Wally Warbles, Phase 1 Death Screen
In this phase, Wally has two primary attacks:
- Trigun finger: This attack involves turning his head into a hand with three fingers shooting three bullets in a spread formation at the player in an attempt to damage them.
- Egg Bomb: His other attack involves shooting eggs in a straight line that break apart upon contact with the edge of the screen. On Regular mode, the egg fragments burst outwards in a spread shot of 3 bullets while it only bursts vertically on Simple mode, and the eggs will burst into five bullets, with the 2 extra shots moving vertically on Expert mode.
After being damaged enough, Wally will begin flapping his wings furiously and firing constant radial bursts of feathers outwards. Eventually, he will tire himself out and temporary leave himself open for attack.
Throughout the first phase, he is accompanied by rows of 3-4 birds, each with a nail tied onto them. The first 2-3 will be yellow, while the last one is always pink and able to be parried. (It is 3 in simple, and 4 in regular).
Once Wally has taken enough damage, he will lose all of his feathers and fall out of the house, after which the birdhouse explodes, revealing his son flying on a small bird nest.
"My dad's the brawn and I'm all brains! Together, we bring the pain."
—Wally's son, Phase 2 Death Screen
In this next phase, Wally's son floats around the screen accompanied by five spiked eggs (four in Simple and six in Expert respectively) that block bullets and revolve around him. The eggs periodically expand and contract around the boss.
Apart from the egg shield, the boss can fire a single electric bullet at the player's direct location, which can be parried.
Once he has taken enough damage, Wally's son will cry out for help and disappear, after which the original Wally appears for a final fight. If on Simple difficulty, his cry for help won't be enough, as the battle just ends.
"Even without my feathers, you're in for stormy weather!"
—Wally Warbles, Final Phase Death Screen
In this final phase, Wally is seen lying on a stretcher, wounded from the last fight and being carried by two blue birds in paramedics uniforms. This phase is not playable in simple. He has two primary attacks to damage the player:
- Trash can attack: His head will turn into a trash can which will spew out objects toward the player. Occasionally, pink boots will be fired, which can be parried.
- Heart attack: He will occasionally stomp his chest with his legs to shoot his heart upwards, which then shoots three bullets in a spread formation before returning down.
The two blue birds will periodically shoot pills up from their beak during Wally's attacks. After a short pause, the pill will split apart with one end targeting the player's location. Occasionally, the pill will be pink, signaling its ability to be parried.
The only vulnerable segment of the boss is Wally himself and his heart. Bombs are nearly required for this stage, however you can inconsistently damage Wally from the bottom of the stretcher.
Once Wally has taken enough damage, he is defeated and left dizzy. The two blue birds eagerly prepare to make a meal out of him by sprinkling him with salt and pepper, with their medic hats being replaced by chef hats.
- Wally is one of the few bosses that are not seen at the ending, implying that he was eaten by the two blue birds who shake salt and pepper on Wally after his defeat.
- He is also the second boss that is implied to be truly dead, with the first being Goopy Le Grande.
- His old line was "I'd say that was more of a crash landing".
- Wally Warbles's son shares similar characteristics with Woody Woodpecker, another popular cartoon character of the 1940's. Warbles himself shares a striking resemblance to the giant bird from Popeye Meets Sinbad.
- Wally's son resembles Woody Woodpecker's early design with the difference being that the eyes are yellow instead of green.
- The fact that Wally Warbles hides inside a cuckoo clock might hint a subtle resemblance to Cuckoo Condor, a boss from Wario Land 4.
- His last name is a play on words on "warbler."
- "Ride of the Valkyries", a composition by Richard Wagner, plays for a brief moment during the song for Aviary Action.
- It's possible that Wally's cuckoo clock form is more than just a disguise as when he does his three-fingers attack or start firing his feathers, cuckoo clock sounds can be heard.
- His eggs look similar to Yoshi eggs from the Super Mario franchise.
- His egg spitting attack is also similar to Birdo's signature attack from the same franchise.