An odd stutter seems to come over people when they refer to The Thing. Not Ben Grimm of the Fantastic Four, with whom they seem to have few if any grammatical problems, especially around Clobberin' Time, but the one in sentences beginning "The thing is".
Not, you might think, the most complex construction. You have a thing. It either is something, or it isn't. If it happens to be a banana, for example, then the thing is a banana. Nothing complicated about that.
So why do we keep hearing "the thing is is the train was late"? Clearly the train being late is identified as the thing. That is what the thing is. One thing is the other. So what in the name of all that's holy is is the second "is" doing there? When people try to write this down, they struggle to rationalise it, resulting in "the thing is, is" and even "the thing-is is". This is because they are twats.