This blog documents the Lego hacks of a young boy, with occasional contributions from his sister and other family members. While a few of the designs illustrated here are simply Lego replicas of existing artifacts, many follow a more inventive design constraint. For example, some attempt to capture a recognizable form in as few Lego bricks as possible. Others transform one "brand" into another (such as the conversion of a Star War ship into a Star Trek one).
That said, the constructions that serve as the closest analogue to software hacking are probably those that exploit ways to attach Lego bricks that bend or break the rules of Lego creation. Such creative misuse permits Lego Hacker to build a bridge from misaligned pieces, or a stable cross from open treasure chests.
This spirit of creative misuse has been key to the history of art and technology of the past fifty years, from Nam June Paik's lugging a magnet onto a TV set to the invention of remote scripting through a hidden iframe hack. Children naturally think outside the box, and I think adults could become more creative by emulating their example.