which tv series has the BEST extended versions (e.g. from the DVD era) ; example; the office has extended scenes for most episodes. Is there any other good series like this?

Friends. The streaming episodes are the chopped up syndicated ones. Well worth it to buy the DVD sets with the full episodes.

The Blu-Ray copies of The Good Place have extended cuts of almost every episode. Hannibal on the US Blu-Ray releases removes all the censorship done to make the series broadcastable on NBC, which isn’t quite the same thing but is still notable.

Lord of the Rings extended editions are movies but they're basically like watching a whole different series with all the extra content. For actual TV shows, Community had some really good deleted scenes and gag reels that made episodes way better Also Game of Thrones had extended episodes in later seasons but those were... well we know how that went lol. The earlier season commentary tracks were pretty solid though if you're into that kind of thing

Since it's so expensive to do that, it's rare. Has to be big show. Office, Parks/Rec, Sex/City, Friends. When I worked in TV, long ago, we had to make longer versions for foreign (in a few cases). I can't for the life of me remember what it was called, drop-in or something. Sometimes they were stand-alone interstitials, but they often expanded a scene. This was to make the show closer to an hour for other territories, since we were making 42-43 minute shows b/c of commercial breaks. That obviously isn't needed for many shows today, but I wonder if the Office or other shows did that as well. Going back to re-edit, re-mix, re-color, re-QC, re-master old footage is not a simple thing. But when we did it, we had to do all of that the first time. Hmm.

Red dwarf season 7

Vikings

M\*A\*S\*H. Also see if you can find the UK release without the laugh track

Just for the DVD menu design, I'm Alan Partridge

Because the old Muppets shows were co-produced by American and British channels and produced in England since that's where Jim Henson actually lived at the time, the UK airings had extra airtime due to not needing to air as many adverts compared to the US; for this reason, they added sketches where the Muppets cover popular songs which became a huge bonus for American video releases.

Caprica and 2000s Battlestar Galactica, every extended version of the stories from that franchise is worth watching.

All of the Simpsons DVD's have great commentaries on every episode and occasionally some deleted scenes.