ThunderCats was a Marvel UK title, initially published weekly from 21st March 1987, later becoming bi-weekly with issue #84. It became a monthly title from #95, but reverted to bi-weekly publication with #105 and remained bi-weekly until the final issue, #129, on 12th January 1991. From issues #79 to #83 the title was briefly changed to ThunderCats and Galaxy Rangers, as it absorbed another, failed title, Adventures of the Galaxy Rangers. A number of specials and annuals were also published. A mix of UK-originated material and American reprints, ThunderCats was based on the American animated TV series and toy line of the same name, about a group of feline humanoids called Thunderians from the planet Thundera, led by the heroic Lion-O, and their efforts to defend Third Earth from the demonic sorcerer Mumm-Ra and his evil mutants. The title also featured back-up strips starring Marvel's child heroes, Power Pack.