ThunderCats (comics) entered the Book of Omens to begin his training and claim his rightful place as Lord of the ThunderCats, but Mumm-Ra uses a powerful spell to keep Lion-O trapped in the book for several years in real time, not "Book" time, and seizes control of Thundera afterwards. In the follow-up mini-series, "The Return" (written by Gilmore and illustrated by Benes, Pimental and Lea), published in 2003, Lion-O returned to Thundera to find it enslaved to Mumm-Ra. Several of the ThunderCats are scattered. Panthro, who was left in charge while Lion-O was away, was forced into slave labor. Tygra and Cheetara
Cartoon Cartoons discontinued and the openings of "Cartoon Cartoons" that were shown before the opening of the actual "Cartoon Cartoons" show was dropped. That same month "Summer Fridays" replaced "Cartoon Cartoon Fridays", making it the first Cartoon Network Friday-themed program block not to feature the "Cartoon Cartoons" names or air under the "Cartoon Cartoons" brand. "Summer Fridays" also featured shows that were not a "Cartoon Cartoons" series and syndicated series that originally aired on other networks, such as "Teen Titans" and "What's New, Scooby-Doo?". "Cartoon Cartoons" also had a jazzy-7-note theme song (composed by Steve Mank). The song was first played in