Not much is known about Yo-Yo, except that he is an inmate at Belle Reve who volunteered to join the Suicide Squad in an attempt to "shave years off his sentence".
He was introduced as the personnel replacement (alongside pre-New 52 veteran Suicide Squad member Captain Boomerang) for Black Spider, who was taken off-duty and evacuated after his mission. Yo-Yo introduces himself and jokes on the nature of his name, "No, I don't have a freakin' string up my ass."
He is one of the people sent to perform a smash-and-grab mission against the terrorist cell Basilisk. He is shown to flirt with fellow felon Harley Quinn, and also first demonstrates his abilities by greatly increasing his mass to protect the team from an exploding henchmen (though he can still feel the incoming heat).
When back at Belle Reve, Yo-Yo is caught up in a supervillain prison riot, tasked alongside Deadshot and El Diablo with quelling the inmate rebellion. He is ordered by Amanda Waller to retrieve King Shark from his holding cell. Yo-Yo uses his ability to slip through the bars, where an otherwise immobile King Shark devours the mass-shifter whole! King Shark lowers his head to stare blankly at Yo-Yo's blood congealing on the cell floor, perhaps feeling regret for what he has done to his fellow team member.
In Suicide Squad #6, however, it is revealed that Yo-Yo is somehow alive inside of King Shark. It is revealed in issue #10 this was part of Waller's plan to determine Yo-Yo's limits. Waller revealed that Yo-Yo is virtually indestructible.
Powers and Abilities
Yo-Yo has the ability to increase his body mass to an extent where he is capable of resisting an explosion in his immediate vicinity, and other damage to a similar degree. In the opposite manner he is also able to decrease his mass, to bypass small gaps and other slight obstacles. One use of this power was to get into King Shark's holding cell at Belle Reve.