You Can't Do That On Television was the show before WTYO happened in February 3, 1979 as it aired on a local channel in Ottawa called CJOH-TV as it had the same cast members on the show and it ran for an hour on Saturday mornings.
The show had comedy skits, opposite skits, locker jokes, green slime, pie in the face, disco dancing, contests and music videos.
Roger Price didn't want any experienced young actors on the show since he wanted just kids being kids. The show ceased on May 5, 1979 and then a pilot episode of WTYO aired nationwide across Canada for an hour a week later as it was trying to introduce a new show to kids and borrowed some skits from YCDTOTV for the pilot and some other episodes and that fall, it aired in prime time hours for twelve half hour episodes (only comedy sketches and musical guests, these episodes were shot in the summer and fall of 1979) then the show got axed on December 1979 since it wasn't a good time slot for a children's show.

YCDTOTV re-aired in the new year of 1981 this time as a network program on Saturday mornings and kept most of the same cast members like Christine McGlade, Lisa Ruddy and of course Les Lye. However, Ruth Buzzi never returned to it since the company couldn't afford to keep her on.
The show was a little different as there were no contests or disco dancing since disco was dying down and the show got more gross but there were more green slime when kids said "I don't know" plus, more opposite skits and the show introduced some new skits too.
Kevin Somers, Jono Gebert, Kevin Schenk and Rodney Helal were still regulars just for the 1981 season. Somers and Gebert were the two oldest in the show and so they took turns on each episode just acting in the dungeon and execution skits since they were getting too old for the show but all four of them were booted off during the 82 season as they reached their height and pursued different careers.
Plus in 82 it only ran for a half hour long on Saturday mornings and then they no longer showed music videos. Alanis Morisette started out on the show in 1986 before she pursued a singing career.
The show was being more Americanised so Nickelodeon bought the rights to the show and the series eventually aired every weekday after school.

Lisa Ruddy left the show in 1985 and Christine McGlade left in 1986 and the show ran for one more season but it was never the same and in 1987 the show was cancelled but however in 1988 they aired on Canadian channel YTV in reruns and decided to air another season by having a contest for viewers with a Les Lye trivia and if they were the winners they would be on the show and they started taping it in 1989.

YCDTOTV was a more successful show but didn't have as good stuff like in WTYO such as the musical guests on the show which made it really entertaining.