This, apparently, is a spoof news item about new trouser fashion. This is a Google translation of the description from the Spygg YouTube account that posted this report. “Spygg” himself apparently used to work at ZTV:

"To see how much influence we at ZTV had on kids, we decided to fake a trending fashion that didn't exist and see what happened. So we came up with the ugliest thing we could think of; having our trousers tucked into our socks, and then we went out into town and asked unsuspecting people on the street what they thought of the new fashion. Surprisingly many pretended to already know about it, even though it was completely made up, and we also met a bunch of celebrities, most of whom (except ABBA's Benny) were in on the joke. Then we cut and broadcast an unreasonably long report about this "new fashion". Imagine our surprise and joy when we started seeing this on the streets the following weeks. It wasn't a huge deal, but some people had bought into it. Success!"

Benny’s bit starts at 00:57, although, bizarrely, it sounds as if his voice has been dubbed by somebody else. He said that he’d never had his trousers inside his socks, but since he’s 51 he should have, at some point in his life. But he’s not aware of this fashion.

A few people with ABBA/Benny connections feature in this report. The reporter is Mats Strandberg, the co-writer of the Circle series of books, the first of which was made into a movie by RMV Film. Johan Renck (Stakka Bo), of ABBA Voyage fame, is interviewed, as is Jonas Åkerlund, who put together the opening film at ABBA The Museum.

Benny was filmed at Skansen. You can see from the clip that he is standing in front of the Björnen (bear) enclosure and was likely filmed at the same time that he and Björn christened the two bears there “Björn and Benny” after a vote by the Swedish public.
 

Thanks to Carl Magnus Palm.
YouTube link c/o PerNormanSpygg