ThunderCats - Season 2 - Eps 19: Day of the Eclipse
With only Lion-O and Snarf guarding the Lair, Mumm-Ra decides this is a perfect opportunity to invade the Lair, so Ma-Mutt captures Snarf and Mumm-Ra switches Snarf and Ma-Mutt. Ma-Mutt (who now looks like Snarf) goes to Cats Lair and gives Lion-O some poisoned candy fruit. Lion-O becomes ill and realizes that this Snarf is really Ma-Mutt and Mumm-Ra arrives and defeats Lion-O. Snarfer's bad dream of Snarf becoming a dog causes him, Ben-Gali, and Pumyra to go to Cats Lair, but Mumm-Ra lays a trap for them. He sends Ma-Mutt to get Snarfer and Lion-O becomes better again and distracts Mumm-Ra. When Lion-O summons the other Thundercats, Snarf (who looks like Ma-Mutt now), using Mumm-Ra's chant that changes Mumm-Ra into the everliving, becomes... Snarf-Ra the everliving and he rescues Ben-Gali, Pumyra and they in turn rescue Snarfer from Ma-Mutt. Then Snarf-Ra challenges Mumm-Ra and defeats him. After the battle is over, Lion-O uses the sword to restore Snarf to his original state.
About ThunderCats

Title: ThunderCats
First Air Date: 1985-01-23
Last Air Date: 1989-09-29
Status: Ended
Rating: 8.2/10 (from 1026 votes)
Language: EN
Seasons: 5
Total Episodes: 130
Network: Syndication
Genres: Animation, Sci-Fi & Fantasy, Action & Adventure, Kids
Production Companies: Rankin/Bass Productions, Lorimar Telepictures
Synopsis
The inhabitants of the planet Thundera evacuate just before it is destroyed. They were pursued by a band of mutants. All but one of their escape ships was destroyed. Only a small group of Thunderans (Thundercats) remained. With only half engine power, the group, which was led by Jaga, had to set a course for the nearest planet. Jaga commanded their ship while the other seven were in their stasis tubes. Jaga died on their journey to Third Earth and their ship crashed there. Soon they made friends with various groups in the area and they designed a fortress. Mumm-Ra the centuries-old embodiment of evil, along with the mutants that destroyed the rest of the Thunderans are a constant threat. But Lion-O, the new leader of the Thundercats, with his weapon the "Sword of Omens" will help the Thundercats to have a standing chance.
Cast

Larry Kenney
Lion-O / Jackalman (voice)

Peter Newman
Tygra / WilyKat / Monkian (voice)

Earle Hyman
Panthro (voice)

Lynne Lipton
Cheetara / WilyKit (voice)

Earl Hammond
Mumm-Ra / Jaga / Vultureman (voice)

Bob McFadden
Snarf / Slithe (voice)

Gerrianne Raphael
Pumyra (voice)

Doug Preis
Alluro (voice)