The 1996-1998 late-night boom was one of the most swift and dramatic shifts in the field in anime history. In 1996, fewer than 40 new anime were broadcast. In 1998, 75 new shows took to the air, and that number continued to grow, with hiccups, until it peaked in 2005.
Not all TV anime airs in neat 30-minute slots, though, and one of the more interesting things I found out about that period while building up a list of which shows over this period were broadcast when was that 18 of the 150-odd shows first aired in 1998 or 1999 were shorts aired on a particular variety program by the name of Wonderful. This program, a 55-minute affair that started 5 minutes before midnight on Mondays through Thursdays, featured comedy, celebrity guests, and an idol group called the “Wonderful Girls”.
Besides its other segments, Wonderful also had a dedicated anime slot; the last 10 minutes of the show, from 24:40 to 24:50, were partitioned out for some kind of short anime for a bit over 2 years (from September 1997 to December 1999) before anime was replaced by drama and other material for the remainder of the show’s five year run. The majority of the shows to air in this microslot were not notable, or in many cases even safe for work.* But, as mentioned, it did feature a total of 18 new shows** over that span. That amount makes it mildly noteworthy, as does the fact that two of those shows were directed by ace pilot Akitaro Daichi.
*NSFW warning, there.
**Counting 3 sequels of existing properties: You’re Under Arrest, Nippon Ichi Otoko No Tamashi 2 (the first and second seasons both aired in this slot), and Yume de Aetara.