Everyone knows that the secret to Java's portability is its bytecode. So long as there is a JVM on your target platform, you can run any valid bytecode with little fuss. But in spite of its well-known benefits, most Java developers don't really understand the bytecode. Apart from the occasional prod or glance under the hood, most of us have happily ignored it. But there are some interesting bits in there and some interesting things that can be done if you understand the bytecode. In this talk we'll walk through the basics of bytecode looking at some various source-to-bytecode comparisons to help unveil these deeper mysteries. And then we'll have some fun abusing that knowledge for fun and profit.