He appeared in the episode "Calliope Dreams".
The Seaclops prefers to sleep every thousand years, but when Ariel's unskilled calliope playing wakes him 600 years earlier, he starts causing havoc across Atlantica. King Triton has to come to the realization that it is the Seaclops who is responsible for destroying the calliope used by his grandfather Neptune.
All of Sebastian's attempts to lull the Seaclops back to sleep result in becoming futile, unable to calm the monster. However, Ariel starts playing the harp that had fallen to the ocean floor that finally lulls the Seaclops back to sleep. As a precaution, Triton relocates the monster to the underwater mountain range far from Atlantica.
In the third issue of the Marvel Comics serial, the Seaclops acts as the main antagonist, having been prematurely awoken again, this time from a dare by the Daredevilfish Club, which results in his hypnotizing the members of the club and manipulating Ariel into stealing the trident as a "dare". He intends to use the trident as revenge towards the Atlanticans for waking him up. Ariel manages to avert the disaster upon realizing what happened, and proceeds to sing him a lullaby, causing him to return to his crevasse to go back to sleep. The issue implies that this event takes place some time after the events of Sea Calliope.