I realise this is a fairly odd question to ask but in recent rounds of hiring we have noticed a rather odd trend in new developers that spectacularly fall short of our expectations. So much so that they to all intents and purposes appear to be an entirely different person to the one interviewed and tested.
We pre-screen applicants during their initial interview with a fairly nasty PHP/MySQL written test which tests both their knowledge of the PHP/MySQL as well as some fundamental aspects of application design. You cannot score highly on this test by simply memorizing the PHP and MySQL manuals (We've made that mistake in the past). I'm sure It is by no means fool-proof, but is intended to be sufficient to weed out those who have clearly lied on their resumés.
Applicants that pass this stage are offered a second interview which is followed by a 2 hour practical test where they are required to develop a small application to a given specification. They are not necessarily expected to complete the task but are judged on their approach to the given task.
Three times now he have hired the "best" applicant based on interview and test results, and each time the person that has showed up for work on the first Monday morning has been completely devoid of the skills and experience they have previously demonstrated. Each of these applicants scored over 90% on the written test and exceeded our expectations when given a practical task to complete.
Hence my coining of the phrase "Developer Twin Syndrome"
Has anyone else experienced a similar trend in hiring developers?