Dre/Pac
This is a captured moment of the only time they were in the studio together for 'All Eyez On Me'. The song 'California Love' was given to PAC by Suge who just had PAC add his vocals to an already completed song, as 'California...' was to be the lead single off of Dre's follow up solo album to his incomparable 'TheChronic'. In regards to their other "coloboration", "U can't C Me", Suge once again took the track from Dre and replaced Ice Cube's vocals with PAC's as this was to be the lead single off the Dre/Cube 'Helter Skelter' project on Death Row Records reuniting the two former N.W.A superstars.
More on Rakim/50/Dre thing
For Rakim's Aftermath debut, 9 original songs (complete with full verses and choruses) produced by Dr. Dre were done and "in the can" ready for mastering. Inexplicably, 2 months later Rakim and Dre had a falling out that led to Rakim getting his release from the label. All of his verses were stripped from those beats and literally 2 weeks later replaced with full verses and hooks by the then newest Aftermath signee, Curtis "50 Cent" Jackson. Two of those former Rakim tracks went on to become, If I Can't and Heat, for 50's debut, Get Rich Or Die Tryin'.
Mike/Suge
With his empire reeling as a result of the death of the Icon himself(PAC), lack of musical vision, and creditors up the arse, Suge was scrambling to find a way to put his newly minted, Tha Row Records, on top by any means necessary and the only way to do that was through good music. Unfortunately for him, ass whuppins for sport and late royalty payments kept a lot of people from working with/for him as they were scared for that to happen to them. Suge felt with proven artists in the stable like Petey Pablo, Juvenille, Kurupt, Crooked I, and Left Eye plus a burgeoning friendship with rapper on a serious upswing, T.I., could produce some good music and have him back on top. The problem was and has always been the use of intimidation as motivation. He lost a valuable piece to his empire when he tried to punk Devanté Swing in front of their mutual friend, Iron Mike Tyson. When Suge threatened Swing with one of those patented 'Row' beatings for sport for not making hit records, Tyson countered with getting up in Suge's face in defense of Swing and admonished Suge for what he felt was Suge's poor treatment of his employees. He informed Knight that a beat down of epic proportions was headed his way if he didn't back off. This in turn allowed Swing the freedom to start showing up at the studio when he wanted to eventually not at all.
This isn't anything revealing... most of this is well documented. Dude been reading a bunch of old Source magazines and documentaries on Death Row.