Song of the Petalars is the fourth episode of ThunderCats 2011 TV series.
As the Lizards keep getting closer to the ThunderCats, Lion-O questions if they're fighting a losing battle. When they see a small armada catching up, they hide in a thorn-bush forest where they meet the Petalars.
The Petalars have lived in the forest since their ancestors were swept away by a powerful wind. Lion-O meets a young boy, Emrick, who wants be a hero like him. Over the course of the journey, Emrick gets older, which Cheetara learns that the Petalars live for what is a day to everyone else, but is a lifetime to the Petalars, who do not know or notice this. Following a map to the "Cliff of Winds", Lion-O wonders what's the point of it all. At the Gate to the cliff, the group is ambushed by three lizards. The Petalars, grateful to the Cats for aiding them on their journey, stun the lizards long enough for the Cats to win. Slithe becomes impatient and orders the forest to be burned down. The ensuing fire causes an updraft, allowing the Petalars to ride and escape.
Emrick, now a dying old man, thanks Lion-O for being his friend and reminds him that what matters in life is how fully we live, before passing away. Now more confident, Lion-O leads the ThunderCats against the Lizards outside the forest. When the lizards are about to end them, Panthro arrives in the ThunderTank and easily dispatches the lizards and their war machines.
- At one point in the episode, Cheetara says "As the ancient Thunderian philosopher said: Time is relative..." In reality, it was Albert Einstein who said that time is relative.
- This is the first episode in which Panthro appears.