A few famous examples to start us off.
Coyle naturally (managed us and Rovers)
Mo Johnston (an infamous one in Glasgow circles, signed for Rangers in 1989, after a spell with Celtic).
Kenny Miller (another who crossed the Old Firm divide on a regular basis)
Denis Law (now I knew he'd famously crossed Manchester in the 1970's, before of course scoring the goal which relegated Utd, but what I wasn't aware of was he also enjoyed a brief spell at Maine Road in the early 1960's)
And lastly one which some younger readers might not be aware of.
Matt Busby (played for Man City in the 1920/30's, before going on to lift the EC with Man Utd in 68).
I'm sure there's countless others, but alas I have to get ready for work, so I'll leave it to you guys to fill in the blanks, and maybe throw up some surprises.
