It was a while ago so I sadly can't remember the exact method but not much more than 5ish years ago, not like 10 years ago. I remember being very shocked that it worked at all and I'm quite certain it wasn't Tiger, I wouldn't have found that very remarkable. I regret not documenting it more now!Are you sure you're not thinking of Tiger? That method of passing to QuickTime or even better RealPlayer or MPlayer was great but couldn't work on OS9 because streaming 3gp wasn't supported.
The YTBrowser for Classilla handed off flv videos before Youtube deprecated that format.