"Return of the Driller" is the thirty second episode of ThunderCats (original series).


It's a race against time for the ThunderCats when Mumm-Ra orders the Driller to bore a tunnel from Acid lake to the Cats Lair.


Wilykit and Wilykat are enjoying themselves, picking apples in the forest. Mumm-Ra, who is observing them from his cauldron, is extremely annoyed that the ThunderCats are thriving on what he claims to be his planet. He summons the Driller and pays him diamonds to bore an underground hole from Acid Lake to the Cats Lair. The Driller complies by burrowing the channel and at once the lake's powerful Ultrasolvic acid starts dissolving the Cats Lair's foundation.

Unaware of the grave danger that they are in, the ThunderCats are carrying on their daily activities as normal inside the lair. As Snarf prepares apple sauce using the apples that the ThunderKittens plucked, the adult ThunderCats are testing out a new "Super fuel" invented by Tygra for the ThunderTank. Suddenly Lion-O detects a foul odor in the lair. Tygra puts the emanation through the analyzer and identifies it as being Ultrasolvic acid. Lion-O uses the Sword of Omens "Sight beyond sight" and discovers that the acid is right under the lair. Tygra suggests that the only substance that can neutralize the acid is Sponge Fog, and so the ThunderCats rush to obtain it.

The ThunderTank soon reaches the valley where Sponge Fog grows. Panthro engages the tank's cutters and carves out a block of the Sponge Fog. As the ThunderCats start to tow the Sponge Fog, Rockmen start pelting the tank with giant boulders from the top of the cliffs. In order to avoid the shower of boulders, Panthro decides to take a detour through the Forest of Giant Insects.

As soon as they enter the forest, the ThunderCats first encounter the Mechanosect and then a giant beetle but the Cats manage to vanquish both the bugs. The tank then abruptly stops due to a fault with its transmission. Lion-O exits the tank to inspect it but is immediately seized in the mandibles of a giant worm. As the worm begins to burrow into its hole, Lion-O manages to grab his sword and summon the other ThunderCats. Panthro, Tygra, and Cheetara attack the worm and it lets go of Lion-O.

Seeing that the ThunderCats had successfully overcome all the obstacles that they had faced, Mumm-Ra decides to delay them himself. He transforms into his ever-living form and flies out of his Black Pyramid. By now, the ThunderCats have reached the Bridge of Light and as they start to cross it, Mumm-Ra flies in and destroys the bridge. The ThunderTank falls into the River of Despair below. After almost being sucked into the Whirlpool of Infinity, the ThunderCats manage to reach the Cats Lair just in time to plug the hole in the foundation with the Sponge Fog and save their home.





  • Much of the scene in which Mumm-Ra summons the Driller and pays him diamonds was reused from Spitting Image, the episode in which Driller made his debut.
  • When the ThunderCats are trying to free Lion-O from the grasp of the giant worm, the brief sequence of animation focusing on Tygra's bolo whip flicking through the air is taken from the show's opening titles.
  • Despite the title of the episode, the Driller only appears for a few minutes in the beginning and is not seen again for the rest of the episode.

Animation Mistakes and/or Technical Glitches

  • When the Lion-O is complaining about the smell of the new super fuel, the part of Tygra's uniform covering his right collar is light gray instead of the normal dark gray. This error is visible again when the ThunderCats are in the ThunderTank.
Return of the Driller error1.jpg

  • When Mumm-Ra first takes the hourglass, all the sand is at the bottom. However, when he flips it over, most of the sand is still at the bottom.
Return of the Driller error2.jpg

  • When Lion-O is being held by the giant worm, his arms are pinned and he is only able to draw the sword out and hold it in his left hand. But when he is summoning the other ThunderCats, both his hands are shown holding the sword. The next shot of Lion-O shows the sword back in the clawshield again.
Return of the Driller error3.jpg

Inconsistencies/Continuity Errors and/or Goofs/Oddities

  • When the ThunderTank stalls, Lion-O gets out of the front seat and goes back to check it. When he doesn't come back after a while, Snarf goes up to look for him. He only looks forward before telling Panthro that Lion-O is gone without even looking in the direction that Lion-O actually went. Then when the rest of the ThunderCats go searching for him, they too all head in the forward direction.
  • When Lion-O summons the other ThunderCats, they all respond to the signal and come to his aid except for the Wilykit and Wilykat.


Wilykat: You made me do that, Wilykit.
Wilykit: No, I didn't. You fell because you broke the law.
Wilykat: Broke the law? Which law?
Wilykit: The law of gravity!

Mumm-Ra: How very charming! What a tranquil scene! The ThunderCats romp and play unmolested on my planet! I shall soon put an end to this frivolity! Be gone, foul image!

Lion-O: You're sure that motor's nailed down tight? If this superfuel is as good as Tygra says it is, it could rip that motor right off the table.
Panthro: Trust me. It'll never leave the table.
Tygra: Ignition!
Panthro: Ignition. [activates it and a jet of flame shoots out the back before it causes the table to take off around the room breaking crates and finally through the door]
Lion-O: You did it, Tygra!
Panthro: [grinning] And like I said, the motor never left the table.

Lion-O: Most of the giant insects feed at night.
Snarf: [whimpering] And me without my bug-spray.

Lion-O: A few seconds more and I might've been living in that wormhole.
Panthro: If we don't get that sponge-fog back in time to save Cats' Lair from that acid, we might all be living in a wormhole.


Black Pyramid, Cats Lair, Acid Lake, River of Despair, Bridge of Light, Forest of Giant Insects


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