Seeing an occasional dip in of a boom mic or the top edge of set wall while watching old, wonderful episodes of the British "The Avengers" series. This occurs because in the era of CRT tube TVs the "overscan" of sets could be depended upon to not show that upper area, so a bit of sloppiness in this respect was common. With modern digital transfers you get the full frame without overscan, which explains these effects.

When you watch episodes of Johnny Carson's "The Tonight Show" now (about which I have a number of personal stories I've told in the past, since I attended quite a few tapings) you will now typically see the boom mike darting in from guest to guest as they speak; this was not visible on conventional CRT TVs.

This is not the same situation as when you see boom mics or other equipment in films -- that relates to aspect ratio/theater projection masking issues, which I'll discuss some other time.