There are two Deus Ex games. The original classic, and the brilliant recent sequel, Human Revolution. Sure back in 2004 there was an ill advised follow up called Deus Ex: Invisible War, but shortly after its release we all agreed that it never happened, and we would never speak of it again.
Warren Spector apparently didn't get that memo. Speaking to IGN during a preview of Epic Mickey he said he regretted listening to the feedback of focus testers when making the game.
“We focus tested concepts." he said "and I was told, 'Set the game further in the future and put the guy or the girl in a purple jumpsuit; people like purple jumpsuits. Why did I listen?”
Who on earth answers a focus test with 'put the guy in a purple jumpsuit?' What kind of questionnaire even asks that? Who could possibly think that was helpful or relevant advice? The mind boggles.
Thankfully Deus Ex did eventually get the sequel it deserved, years later and without Spector's involvement. You can find out why it works in our Deus Ex: Human Revolution review .