MIT also has a long tradition of pranks, which are called "hacks" at that institution. Many hacks involve placing an item on MIT's Great Dome or otherwise altering, such as moving a campus police cruiser to its roof, placing full-sized replicas of the Wright Flyer and a firetruck on top of it to acknowledge the anniversaries of first powered controlled flight and the September 11th attacks respectively, and converting it into R2-D2 and a large yellow ring to acknowledge the release of ' and ' respectively. A famous off-campus hack involved MIT students inflating a weather balloon labeled "MIT" at the 50-yard line at the &lt;a href="Harvard%E2%80%93Yale%20football%20rivalry"&gt;Harvard/Yale football game&lt;/a&gt; in 1982.