Buttner says the tradition of any new teammate singing a song in front of the squad was given a twist by the Japanese.
"At United, for example, there is the tradition that you give a speech or sing a song if you are new," he told Voetbal International. "I have held a chat about my first positive experiences at the club, but my buddy Shinji Kagawa found things a bit more difficult.
"He barely speaks English, so he went into the middle of the restaurant of Rio Ferdinand, while the whole squad looked at him when he cried, 'I do not speak English', then the music came on and he danced on his own. Gangnam Style. Everyone was under the table with laughter."