Why is Opera on my mac?

In safari preferences I see a option to choose default web browser and I click it and I see Firefox and Opera browser and it is installed on my mac. But I never even downloaded Opera, Does it come standard with Leopard or something?

No, it doesn't come standard. Perhaps somebody installed it without your knowing?

I figured out that Opera was installed with Adobe CS3. Thanks anyways guys.

Yes, there is a thread somewhere on Mac Forums with another user that had Opera appear out of nowhere and it came from the Adobe installer. Glad you figured it out.

Yeah I have it on my mac mini which has CS3 but not on my macbook which is CS4

Thanks for the info - Answered my question.
It appeared for me after a cs4 installation... as the default program for torrent files? Thx adobe.