As funny as that might have been no it is not a South Park reference. Twice I have seen the phrase "Semper Exploro" which means "Always Exploring". Exploro sounds like an interesting screen name and thus it stuck.
Greetings to all: I am Exploro. I've been playing KSP for roughly two years now and thought it was the right time to join this community. It's a pleasure to meet you all.