This was my case. I was playing around with Linux, both on my own machine at home as well as with a server at my high school (shell accounts being a perk of joining the computer club). While learning about Linux I also picked up some of the history of UNIX. At some point I learned that you could get a copy of x86 Solaris 7 for for < $50 (I can't remember if this was an educational offer or a developer network offer). But I ordered one and was really excited to get to use a real UNIX. I played with it for a while, but ended up going back to Linux for my own computers. Later, in the last year and a half of undergrad and my first year of grad school, I used a Sun Ultra 5 to do the work for and write my first published paper and do much of the work that would end up becoming my MS thesis and my second paper (with some of the heavy lifting outsourced to an Ultra 10 that a postdoc in the research group was using).
Every few months I browse ebay and look at SPARC machines. Though it's not really practically useful, I think it would be cool to have an Ultra 5 again.