On this exact day in 1975, while Pink Floyd was in the studio recording Wish You Were Here, they got an unexpected visitor... Syd Barrett.
There have been multiple Pink Floyd specials on VH1 and I think they talked about this in one special called "Which One's Pink?" - In any case, here's what happened at the studio that day...
The band was in the middle of listening back to "Shine On You Crazy Diamond" when an overweight man with no hair (including eyebrows) walked into the studio. He was jumping up and down brushing his teeth. At first they had no idea who he was.
It took awhile to realize that it was their old friend and former bandmate Syd Barrett.
(Talking about it in this TV special, Roger Waters and David Gilmour said they both started crying.)
Syd wanted to know if he could do anything to help, despite the fact that he hadn't seen his bandmates in 5 years plus the album was almost finished.
I think the whole Syd Barrett story is quite disturbing. It's very interesting though. Go look on his Wiki page and you'll get kind of creeped out.
He died just three years ago, however Roger Waters has said that the band had done all their grieving for him back when they kicked him out of the band due to his erratic behavior (primairly due to psychadelic drugs).
P.S. If you want to see a picture of what Syd looked like that day when he roamed into the studio, then check out this link: http://www.neptunepinkfloyd.co.uk/gallery/main.php/v/SydBarrettPhotos/After-Fame/aau.jpg.html I'm not posting the actual picture on here because it is kind of disturbing. Just warning ya!
P.P.S. Here's "Wish You Were Here" from David Gilmour and the late, great Richard Wright (go to :30 if you want to skip the annoying audience applause!):