Perry is, of course, the best part of this show.  Who doesn't want to be a spy.  Of course, if I were he I would find a cooler cover story than being the pet of two hyperactive dorks and their bitchy older sister.  Also, given that Doofensmirtz seems to know exactly who he is and where he lives, why does he feel the need to maintain the subterfuge.  

I remember playing Top Secret as a kid (the RPG).  It was fun, but in most cases it turned into just another battle game.  Given that we were in jr. high school, the subtle nuances of being a spy and subtly investigating someone were kind of lost on us.  We found the best way to investigate a building or company was over the corpses of the security guards, employees, cleaning staff, and/or (more or less) innocent bystanders.  

If you want to become a spy (and really, who doesn't?) I found some instructions on how to become a spy here.  Seems like a lot of work.  Also doesn't seem like they make a lot of money until they do it for years and eventually turn traitor.  Then they become insanely rich.  

I found another article on real life spy stories that is pretty cool.  Some bad language but really interesting.  I particularily like the Boer guy who hated the British.  A real life bad ass.