With the rise of mature programming language runtimes and vast open source software library ecosystems, designing a programming language and environment from scratch becomes less and less practical from the standpoint of acquiring a user base. Scala and Clojure have demonstrated the power of piggiebacking on the Java Virtual Machine, and the meteoric rise of compile to JavaScript programming languages have shown that a parasitic approach to programming languages may have many years if not decades of viability. We examine the benefits and tradeoffs associated with this approach with a special focus on the Clojure and ClojureScript projects to which I’ve contributed heavily over the years.