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 Network original character, a muscular teenage robot named TOM. During that same year, a series of bumpers featuring the instrumental Powerhouse were introduced. These bumpers lasted from 1997 to 2004. One new original series premiered in 2000: "Sheep in the Big City". On April 1, Cartoon Network launched a digital cable and satellite channel known as Boomerang, which was spun off from one of their programming blocks that featured retro animated series and shorts. Three new original series premiered in 2001: "Time Squad", "Samurai Jack", and "Grim & Evil". On June 18, Betty Cohen, who had served as Cartoon Network's president