There it is, the mischievous yo-yo! Yo-Yo Up, Yo-Yo Orbit, Break Spin, Walk the Dog—it's all child's play! Add an attribute to make it even more powerful, With a variety of moves at your disposal, looking cool has never been easier.”
When Kirby becomes a yo-yo trick-master he wears a backwards purple cap (differentiating from the Wheel ability's red cap) and wields a typical red and white yo-yo as his weapon. In Kirby Star Allies, Kirby's cap now has white on the back with a purple star, similarly to Wheel's cap from Kirby: Triple Deluxe. He also gains a bandage on his right cheek.
Kirby combines break-dance moves with yo-yo tricks as means of attack with this ability. His basic attack involves throwing his yo-yo as a projectile in any direction. This isn't all he can do with it, as he can also grab his enemies with his yo-yo and drop them to deal huge damage, or use his yo-yo to do a showy spin jump. In a pinch, he can retreat or move forwards with a Break Spin.
Kirby throws his yo-yo out which damages any enemy who comes into contact.
Break Spin/Jump Spin
Dash + B
Kirby spins on his head while dashing forward. If done in the air, Kirby has more momentum and does slightly more damage.
10 (grounded), 12 (aerial)
Up throw attack/Yo-yo Up
Up + B
Kirby throws his yo-yo in a small arch upwards, damaging any enemy who comes into contact with it.
Down throw attack/Yo-yo Down
Down + B
Kirby throws his yo-yo in a small arch downwards, damaging any enemy who comes into contact with it.
Forward/Up/Down + B (Near enemy)
Kirby grabs enemies or mid-bosses (the latter only when defeated), and drops them hard enough to destroy them.
Down + (Up + B together)
Kirby spins around in the air, using his yo-yo as a weapon, and damages any enemies that come in contact with him. After the move, he is left vulnerable. At the highest point of his attack, the two stars that spin with him go opposite directions, and have the range to hit both Twin Woods if used in the center.
26 (going up, stars); 6 (going down)
Walk the Dog
Down + (Press and hold B)
Kirby holds his yo-yo in place on the area directly in front of Kirby. The yo-yo will stay in place, even if (without moving) Kirby raises up or falls down, although the yo-yo will come back to Kirby if it strays too far away from Kirby.
Walk the Dog + Foward/Backwards
After performing Walk the Dog, Kirby can move both left and right while still holding B. If Kirby is some how seperated from his yo-yo, as long as the yo-yo is within the vicinity of Kirby, you can still move both yourself and the yo-yo.
The yo-yo, the ability cap, and the background of the ability picture are all direct references to EarthBound. The background depicts EarthBound's menu screen, and the yo-yo and ability cap come from Ness, who wears a remarkably similar cap and often uses a yo-yo as a weapon. This can be seen as an example of HAL referencing one of its own other games, because HAL was a co-developer of EarthBound, along with Ape (later known as Creatures, Inc.).
When Kirby inhales Ness in the Super Smash Bros. games, he wears Ness' sideways hat backwards, as if it was the Yo-Yo hat. Coincidentally, both Kirby and Ness are voiced by Makiko Ohmoto.
Although the Yo-Yo ability was almost certainly intended as a direct reference to EarthBound, the idea of a yo-yo being used as a weapon was originally popularized in Japan by the Sukeban Deka manga series and its film adaptations.
Yo-Yo Kirby's hat is the same as those of Paint and Wheel Kirby's hats, but in a different color (Paint's is gray, Wheel's is red).