After Panthro’s introduction at the end of last week’s filler episode, we get to find out the backstory between he and Grune before the series premiere. In that backstory, they were inseparable friends serving under King Claudus as they fought together against the Lizard Men. They also oversaw the training of both Lion-O and Tygra when they were young until they were called for a mission to search for the Book of Omens by King Claudus. Before they go, King Claudus tells them that Lynx-O is promoted to the rank General over both of them. While Panthro complies, Grune wasn’t happy about it. This was the seed that lead to Grune’s betrayal of the Thundercats. During the journey, Mumm-Ra called out Grune and had him turned on Panthro and it was the last time they saw each other until now. In a way, we’re seeing Grune’s viewpoint on why he did what he did in the series premiere.
Then, there’s the rocky relationship between Lion-O and Panthro as Lion-O thinks Panthro’s loyalty to his father is exaggerated due to his gruff demeanor while Panthro’s loyalty isn’t earned, but eventually Lion-O does so when he takes on the robotic Driller, who looks like a Transformer from the original Transformer. All this when they search for the Thundrillium, which powers up the Thundertank. Wilykit, Wilykat, and Snarf were left on the Thundertank as this removes them for the rest of the episode.
The flashback also has King Claudus on what he was like before the series premiere and how Mumm-Ra was free from his imprisonment. Tygra’s old self from the series premiere is still there while Cheetara is absolutely loyal to Lion-O. This was a much better episode than last week’s and the spotlight was on both Panthro and Grune, but Panthro most of all because he is an important part of the Thundercats. With Panthro serving under Lion-O like he did his father, the entire Thundercats are truly on the loose.