Yacker's basic shape is that of a sphere with three tentacles, two of which are used as arms. He has one pink eye in the center of his head, and two very alien-like antennae on top of his head. Yacker's most distinguishing feature that sets him apart from the other White Wisps however, is a strand of curly blue "hair" on his head between his antennae.
In Sonic Colors, Yacker and a Cyan Wisp are running away from Cubot and Orbot, who are trying to capture them. Sonic, seeing everything, saves Yacker and the Cyan Wisp just as Cubot was about to catch them. He eventually makes his way to Tails while Sonic was checking out the place. When he met Tails, he was trying to tell him something but Tails couldn't understand because Yacker can only make chattering noises. Tails decides to make a translator to understand him. While Tails was making it, Sonic comes and sees Yacker. Tails explains that Yacker can help them (note that they do not know his name at this point). Sonic agrees with Yacker's help but only if Tails can get the translator right. However, the translator seems to be not so accurate with Yacker's language, sometimes translating Yacker's language with silly phrases. However, when it is translated right, Yacker could tell if it's translating right. After a little transitions, they learn his name and get a little idea on the Wisp Power. He then stays with Tails for the remainder of the game as he is mainly seen with Tails and not Sonic, but when they see each other they have a nice greeting. In the dislike for Eggman, he calls him "Baldy Nosehair", which Sonic and Tails find very amusing and funny. This gave the idea for Sonic to call him "Baldy McNosehair" and Tails said he found it so funny that he "wrote it down".
At the Asteroid Coaster, Yacker disappears for unknown reasons, which leaves Tails and Sonic to worry that he might have been captured and turned into a Nega Wisp. He reappears back at the Tropical Resort. Yacker, along with some of the Wisps Sonic saved, are seen having a party, with Sonic and Tails as the guests of honor, but the party is soon crashed when Eggman begins to fire his mind-control cannon and the Wisps, including Yacker, run away. After Sonic failed to outrun the black hole, Yacker is seen with a few other Wisps, who carry Sonic back to his world. Yacker then flies into space, changing all the Purple and Violet Wisps back to their normal forms and gets them to stop the black hole. Afterwards, Yacker returns to Sonic and Tails to thank them for their help, gives both of them a high five, and leaves with the other Wisps and their planets.
In the DS version after completing the main story, Sonic and Tails, through unknown means get back into space, and find Yacker, who tells them about what Eggman did to his mom, so Super Sonic saves her, and they return to their home worlds.
Other game appearances
Mario & Sonic at the Sochi 2014 Olympic Winter Games
During the "Birthday on Windy Hill" event, Yacker returned to earth to celebrate Sonic's birthday, but got kidnapped along with Chip and some Chao by Dr. Eggman when he trashed the party with his Death Egg drones. Much to Yacker's joy, Team Sonic soon after freed them and he gladly offered any he could. Once Sonic got back from defeating Eggman, Yacker wished him a happy birthday in his incomprehensible language.
Like other White Wisps, Yacker is very sociable and friendly. He has a generally happy attitude and enjoys talking and playing around. He also cares very much for his friends and family, showing general worry when his fellow Wisps were captured by Eggman and sadness when he had to leave Sonic and Tails.
Yacker is rather big on body language, often casually mimicking other people's body movements, or using his own movements to illustrate other subjects in an energetic, yet direct manner.
Powers and abilities
Yacker is able to levitate in midair at will, which serves as his main method of transportation.
As a trait shared by his species, Yacker is able to generate and store his own unique variant of a powerful energy known as Hyper-go-on inside his own body, which is his life source. It is unclear to what extent Yacker can use his own Hyper-go-on, through he has been shown being able to use it to revert Nega-Wisps back to normal, carry objects through levitation, teleport objects and restrain black holes made of Hyper-go-on.
Yacker is able to pass on a fraction of his Hyper-go by phasing into the recipient. When organic beings or robots receive his Hyper-go-on, they can use the Boost to pass through enemies as a living projectile and move at higher speeds.
Yacker, along with the other Wisps appeared in the Archie Comics' Sonic Colors comic adaptation in Sonic the Hedgehog #219. He basically did the same thing like he did in the beginning of the game, which is to say something and Tails works his translator to understand him. Sonic saved him and some other Wisps, and they embarked on their journey to save the rest of the Wisps from Dr. Eggman.