[James2001]

Looking at the Mr Blobby video, during the Shakespear's Sister spoof bit, you can see bits of another picture around the extreme edges of the frame, like what you get on TOTP itself when there's about to be a picture transition of some kind (it's on all 4 showings of the video, so it's clearly part of the video itself, not something going on in the TOTP gallery). There isn't a picture transition following it though, so presumably it's some artifact from the editing process that they wouldn't have expected to be noticed at the time because of overscan.

There are a few music videos out there as well where the faux-letterbox bars don't entirely cover up the picture at the extreme edges- again something that wouldn't have been noticed due to overscan. Something that gets lost now with music videos rarely being seen in their correct aspect ratio- I'd personally prefer them being left alone even if it does leave black bars around the entirety of the screen.