Monday morning code is this kind of code, where you write some seemingly easy code in hour just before first coffee and your co-workers need at least the rest of the week to figure out what went wrong. You would deny this code until you see the blame in svn, after that you start to believe in global conspirators.
Here's some java code I tracked down which caused some ugly bug
// determine objects to copy
MyClass sourceObj = getSourceObject();
MyClass destObj = getDestinationObject();
// copy now
destObj = sourceObj;