In January 1998, UPN began discussions with The Walt Disney Company to have the company program a daily two-hour children's block for the network, airing on weekdays and Sunday mornings. Attempts to reach a time-lease agreement deal with Disney were called off one week after negotiations started due to a dispute between Disney and UPN over how the block would be branded and the amount of E/I programming that Disney would provide for the block; UPN then entered into discussions with then-corporate sister Nickelodeon to produce the new block. That February, UPN entered into an agreement with Saban Entertainment – which distributed two series recently aired on the UPN Kids block around that time, Sweet Valley High and Breaker High – to program the Sunday-to-Friday block. In March 1998, UPN resumed discussions with Disney and the following month, The Walt Disney Company and UPN came to an agreement to provide Disney-produced programs on the network on weekdays and Sunday. The block was originally announced under the working title "Whomptastic", though the name was changed prior to the debut of the block for greater brand identity. The new lineup was later renamed Disney's One Too in July 1999, formatted to serve as a competitor block to ABC's existing children's block Disney's One Saturday Morning. The block debuted on September 6, 1999, replacing UPN Kids, which ended its run the day before after four years. Compared to the format of One Saturday Morning, One Too varied in that, instead of incorporating hosted segments, short gag segments from the shows featured in the block were usually shown, often preceding the start of each program, and after commercial breaks. The block also featured a different opening sequence, using more futuristic buildings and a theme similar to that used on One Saturday Morning. Many shows previously aired on One Too continued in reruns on Toon Disney and Disney Channel. In September 2002, the One Too branding was discontinued as a result of the rebranding of the ABC block from One Saturday Morning to ABC Kids; although the UPN block was not revived, the Disney.com website referred to it under the title Disney's Animation Weekdays. The block aired for the final time on August 31, 2003, with the time periods being turned over to UPN's affiliates; this left UPN as the only "big six" broadcast television network with no children's programming. UPN was not the first "big six" network to pull children's programming: NBC became the first to remove kids shows entirely in August 1992, when the network launched a live-action block for teenagers called TNBC; children's programming returned to NBC in 2002, through a time-lease agreement with Discovery Kids. In the years since the block was discontinued, all other major broadcast networks, including UPN successor The CW, would gradually abandon children's programming by selling their respective children's blocks to Litton Entertainment, who produces primarily unscripted E/I content targeted primarily at teenagers, or in the case of Fox, removing children's programming entirely. Fox's sister network, MyNetworkTV, has never supplied children's programming as part of its lineup; both networks leave the responsibility of acquiring E/I programming to the affiliates, primarily through the syndicated block Xploration Station in the case of the former.
