Sir Paul McCartney didn't realise he appeared on 'FourFiveSeconds'.
The Beatles legend worked with Kanye West and Rihanna on the song but didn't recognise it as something he'd recorded while "knocking around" in the studio with the 'Bound 2' rapper.
He said: "I got a call, somebody said, 'Kanye would like to work with you.' So we just knocked around for a few days and he recorded any little thing we did. In the end, I thought we'd just knocked around and chatted a lot and I'd played a couple of things.
"Then suddenly in the post I get this Rihanna record and I thought it was great but I had to ring up and say, 'What's this got to do with me?'
"Kanye said, 'Well that's you on guitar.' I didn't recognise it cos they'd sped it up.
"And then there's a sort of Mickey Mouse voice on the middle and that's me. I really liked that."
The 73-year-old musician also features on Kanye's controversial track 'All Day' and joked he was tempted to claim he had written the lyrics himself after being advised to distance himself from the song.
He told Q magazine: "On 'All Day', I'd played a little sort of rural, very simple riff and he turned it into an urban monster riff with the n-word about 40 times.
"Some people said to me, 'You can't be associated with this. This is racist.' I said, 'Well, I actually contributed to the music. Kanye did the lyrics, they were nothing to do with me.'
"I must admit, I was tempted at one point to say, 'Yeah, these are my latest lyrics' and take credit for them. Just to put the cat amongst the pigeons."
Paul enjoyed his time working with the "eccentric" rapper.
He said: "He's an artist and he's eccentric but he's a great guy.
"It was a great pleasure working with him. You're on your toes."