Hey, I was a strike away from throwing a 900 series once......then the damned cat jumped on my head and woke me up.
Seriously though, I once threw a 696 in league bowling (with a 244 in my practice game). I couldn't do ANYTHING wrong that night, but a 700 is quite an accomplishment.
I used to bowl with Mark Roth (since grade school) and he'd pound out 750's regularly (long before turning pro).