ThunderCats (1986)
Cartoon Series: Season 01; Episode #01: "Exodus"
Thundera. A world about to die. A victim of it's own sun, the planet is about to explode. Jaga, the wisest of the thundarian race, arranges for a massive exodus before this can occur. Upon leaving thundera, Jaga's vessel is separated from the remainder of the fleet, and finds the ship is on a direct course for a planet called Third Earth, but it will take several years for the ship to reach its destination.
Jaga is an old man, and will soon pass on, before he does so, he gives his crew, which includes the young prince Lion-o, the weapons and powers they will need upon touching down on third earth. He also gives Prince Lion-o the ancient sword of Omens. The thundercats are placed in cryogenic storage by Jaga, and years pass, finally, the ship lands on thundera, but Jaga has died.
Alone, the thundercat crew, now with lion-o a grown man, and their leader, must face the perils that third earth brings, beginning with the evil Slyth and his mutants, ancient enemies of the thundercats, who have pursued the cub heroes to this world for a showdown.
ThunderCats (1986)
Cartoon Series: Season 01; Episode #05: "Trouble with Time"
There is one where Tigra becomes old in the cave of time and has to bathe in the "Geyser of Life".
ThunderCats (1986)
Cartoon Series: Season 02; Episode #17: "Time Switch"
Liono is exposed to time-affecting gases and slowly regresses to infancy.
ThunderCats (1986)
Cartoon Series: Season 02; Episode #26: "Thundercubs' Part 1"
Mumm-Ra learns about the Treasure of Thundera and the Sword of Plundarr (Jaga had beaten Ratilla, who owned the Sword, and then buried the sword deep underground), and he and Ma-Mutt "travel back in time and space" to explore the debris of Thundera and look for the sword, which causes the planet to reform.
The Thundercats find out about this and must make the journey to New Thundera to stop Mumm-Ra. Lynx-O and the Thunderkittens are left at the tower while the other Thundercats at the Lair are preparing the Feliner for the trip to New Thundera.
Vultureman notices that the tower is only guarded by 3 Thundercats and goes to Sky Tomb and tells Luna. Luna then sends Red Eye and Tug Mug to attack the Tower, and they capture Lynx-O and the Thunderkittens.
-- Jeffr_2bya
ThunderCats (1986)
Cartoon Series: Season 02; Episode #27: "Thundercubs' Part 2"
Lion-O and the other Thundercats arrive and save Lynx-o and the Thunderkittens from Red Eye and Tug Mug. The Thundercats learn more about New Thundera, especially the dangerous places affected by the moons of Plundarr where the Lunataks come from.
The Thundercats must develop special equipment and clothing to counter those dangers. Also, they learn that all the snarfs have been turned into slaves and Snarf and Snarfer want to rescue them no matter what the cost. Vultureman learns of the Thundercats plan, so he abandons the other Mutants and takes the Rat-Star.
But Slithe has snuck aboard. Right after the Feliner takes off, the Rat-star ambushes them and it seems all over for the Thundercats aboard the Feliner. Lion-O uses the sword to free everyone and along with Ben-Gali and Wilykit on the HoverCat, go after the Ratstar and it crashes on Hook Mt.
-- Jeffr_2bya
The Thundercats leave Third Earth's atmosphere and Lynx-O tells him that Mumm-Ra has already located the Sword of Plundarr.
ThunderCats (1986)
Cartoon Series: Season 02; Episode #28: "Thundercubs' Part 3"
Mumm-Ra retrieves the Sword of Plundarr and the Thundercats arrive on New Thundera. While the Thundercats want to get the Sword and treasure, Snarf and Snarfer want to free their fellow snarfs. While the Thundercats sleep, Snarf and Snarfer sneak away, but are discovered and captured by Mumm-Ra.
He disguises himself as Snarfer and he leads the Thundercats to where the treasure is located, but it can only be freed by the Sword of Omens. Once the treasure is freed, Mumm-Ra reveals himself and defeats the Thundercats with the Sword of Plundarr. Now Mumm-Ra possesses the Sword of Plundarr and the Treasure of Thundera.
-- Jeffr_2bya
ThunderCats (1986)
Cartoon Series: Season 02; Episode #29: "Thundercubs' Part 4"
Mumm-Ra tries to get away but the Sword of Omens breaks open the casket dropping the treasure all over the planet, and Snarf, Snarfer, and one other snarf escape. Mumm-Ra gives a false Book of Omens to Ma-Mutt, Slithe and Vultureman, who have arrived on New Thundera in the Rat-star, for safe keeping so that he can decipher the real Book of Omens.
The Thundercats go after them through the Caverns of Cold. They head toward the Canyons of Youth, but due to the effects of the canyon, Panthro, Cheetara, Tygra, Snarf, and Snarfer are changed into Thundercubs.
Lion-O must use the sword to give the Thundercubs Thundercat understanding. Meanwhile on Third Earth, Jackalman, Monkian, and the Lunataks attack Cats Lair and capture Ben-Gali and Wilykit. Lion-O learns that the Thundercats back on Third Earth are being held prisoner in Sky Tomb, so he decides to send the Thundercubs to Third Earth to rescue them while he tries to get the Book of Omens from Mumm-Ra.
Snarf decides to stay with Lion-O and the other Thundercubs prepare the Feliner to leave New Thundera but Mumm-Ra arrives and attacks the Thundercubs.
-- Jeffr_2bya
ThunderCats (1986)
Cartoon Series: Season 02; Episode #30: "Thundercubs' Part 5"
Lion-O frees the Thundercubs from Mumm-Ra's spell and the Thundercubs safely leave New Thundera. Lion-O and Snarf must confront Mumm-Ra and get the Book of Omens.
After they defeat Mumm-Ra, they ask Mu-Mutt (using a magical flute) to use Mumm-Ra's "device" to get them back to Third Earth. Meanwhile the Lunataks capture some Berbils and the Thundercubs return to Third Earth and they and the Thunderkittens must go to Sky Tomb to free the other Thundercats and the Berbils.
After everyone is freed, they are all cornered by the Lunataks, but Lion-O and Snarf arrive to save the day. The Thundercubs must then go in the Cave of Time to become Thundercats again and Mumm-Ra is abandoned on New Thundera and the Ancient Spirits bring him back to Third Earth.
-- Jeffr_2bya
ThunderCats (1986)
Cartoon Series: Season 02; Episode #37: "Return Of the Thunder Cubs"
Mommra sends Cheetara, Panthro, and Tigra sprawling into the Valley of Youth to
regress them in order to manipulate them.
ThunderCats (1986)
Cartoon Series: Season 02; Episode #55: Malcar
Mumm-Ra summons Malcar, an ancient alchemist, to return from the dead. The alchemist returns old and weak, as he was when he died. Mumm-Ra takes him to the forest of youth to restore his youth and power. Malcar regains his powers, and uses them against the Thundercats. He transforms all the Thunderillium on the planet into Thundrainium.
-- TBTC
Thundercats (2011)
Cartoon Series: Season 01; Episode #04: "Song of the Petaliars" (08/30/2011)
While traveling through the woods, the ThunderCats come across a group of Petalars - small plant-like creatures whose lifespans are only one day. Lion-O befriends the young Emrick as he and the others try to figure out a way out of the woods and return the Petalars to their home. Meanwhile, Slithe and his lizard army are hot on the ThunderCats' trail to eliminate them. (M/f Creature aP)
-- Jeffr_2bya