There's something I've noticed on a few things I've watched online (and coincidentally they're all Muppet productions). I've noticed that sometimes when a scene transitions at the very side of the screen we see video of something else, usually what comes before or after that transition. I guess it's frozen there.
I first noticed it in a Sesame Street clip, where Kermit asks the Three Little Pigs how they all feel about their houses being blown down. For some reason, this particular clip has the News Flash logo slide up instead of fading to the next scene, and before it fades we can see part of where Kermit is following the title card. And I've noticed this in the clip when viewed in sesamestreet.org and Sesame Workshop's YouTube channel, so it's not like it only happens in fan-uploaded videos. Though it's not there in the iTunes release of an episode with this segment (and that episode does have the same logo card used in the sesamestreet.org copy).
And I've noticed it in Rock Music with the Muppets during the transition to "Don't Blame the Dynamite". Not just on Daily Motion, but also in the promos for the Playhouse Video series as seen on YouTube (yes, that promo actually shows a scene transition that appeared in the video).
And most recently on YouTube, I've noticed it in Sesame Street All-Star 25th Birthday: Stars and Street Forever during much of the Worm TV sequence. It goes away by the end of the "My Name" clip, then comes back during the "ABC Disco" clip, and then goes away before the "A New Way to Walk" clip. And unlike the other examples I've just mentioned, it looks like this footage at the side of the screen is moving a bit, and it doesn't seem to be anything that comes right before or after the transitions. I can't tell if it's footage of the street, Corbin Berensens office, "Do De Rubber Duck", or something else (could it have been from a commercial break if the commercials were cut from the copy used on YouTube?).
Anybody know how this happens?