Tunnels (とんねるず) was arguably the most hilarious and sometimes outrageous comedic act that burst out in the 1980s. I can say that the taller half of the duo, Takaaki Ishibashi（石橋貴明）, probably grabbed the baton from nutty comedian Ken Shimura（志村けん）in terms of pushing what was OK on TV at the time. And both him and his partner, Noritake Kinashi（木梨憲武）, often put forth the personae of the amiable-but-deceptively-condescending superstars in their various skits.
However, I think the above segment which begins this video is Taka and Nori just being darn silly with a whole bunch of other geinojin.
Anyways, I think I may have been watching one of the episodes from their very long-running Thursday night show on Fuji-TV, "Tunnels no Minasan no Okage deshita"（とんねるずのみなさんのおかげでした）back in my Japan days when the guys came up with a brainwave of sorts. Supposedly, there was a skit on the show which parodied Taka-chan's other TV show, the music program "Utaban" (うたばん) on TBS, in which the Tunnels with a bunch of production staff as backup dancers did a song-and-dance a la Kinki Kids.
The skit was a smash with viewers and after that, one thing led to another, and the group Yaen（野猿）was born. Yaen had Tunnels and two other staffers from the costuming and set departments as the main vocalists while several other employees provided the dancing. According to J-Wiki, Ishibashi named this new group Yaen (which means wild monkeys, by the way) after coming across a love hotel named Hotel Yaen on the Yaen Highway in the Tama district of Tokyo one time (no word on whether he actually used it). The hotel has since changed its name to Festa Resort Yaen.
With some training and dressing, the group which numbered around 11 recorded their debut single for release in April 1998, "Get down". And strangely enough, it didn't quite sound like a parody of a high-energy pop song. It actually was a high-energy pop song. I was having a talk with Marcos V. on the recent globe piece about a Japan Times article which related about the good old days of Tetsuya Komuro's（小室哲哉）cool-if-somewhat-cheesy music, and I think "Get down" kinda straddles that line between pop and parody.
"Get down" set the template for Yaen's brief time in the spotlight as an expy of sorts of song-and-dance groups such as Exile. Seeing Tunnels and these production staffers sing and dance themselves on stage automatically had my don't-take-it-seriously alert light flashing off in my brain but at the same time, everyone was going at their jobs pretty earnestly. So the performance actually came off as looking surprisingly polished. It also didn't hurt that it was made by a couple of veterans in lyricist Yasushi Akimoto (秋元康...Onyanko Club, AKB48) and composer Tsugutoshi Goto（後藤次利）who had helped make a number of hits for Shizuka Kudo（工藤静香）among other singers some years earlier. Plus Sam of TRF fame choreographed the dancing.
The song got up...all the way to No. 10 on the charts and later became the 20th-ranked single of 1998. There would be ten more singles before Yaen called it quits in 2001. Apparently, some of the guys were being transferred to other departments.