He was the one who would crack his knuckles like that, and Kaneki, after being tortured by him for days, subconsciously picked up the habit. It was during the torture that Kaneki accepted his ghoul nature, essentially accepting a more violent and powerful side of him as a real part of himself.
Kaneki's nails turned black because of his blood. Before you give up on me, please read on. His nails turn black because his nails died and the blood, below his nail, were trapped there and dried.
In the anime “Tokyo Ghoul”, Yamori cracks his finger every time he tortures Ken Kaneki. This teaches him to crack his own fingers after his escape.
He might have done it during the Yamori Clan't attempted ambush of the Quinx Squad, but we were only shown the end of Haise's fight with Shousei and Hooguro. Haise only does the finger-crack when he's confronting his memories/using more of this kagune.
Kaneki's memories return during the CCG raid on the Tsukiyama family. The raid begins in episode 10 and ends in episode 12. His memory actually returns fully in episode 12.
Hell's Gate National ParkWhen visitors to Hell's Gate National Park reach the sweeping cliffs carved by a prehistoric lake that gives the park its name, they'll discover that Pride Rock's real-life inspiration is no less majestic. Hell's Gate National Park is located roughly two hours from Nairobi.
Dave Thomas, the founder of Wendy's, was an orphan immediately after his birth in 1932 in Atlantic City, N.J. Thomas never knew his birth parents and was adopted by a couple from Kalamazoo, Mich. (Her nickname was Wendy.)