Leonard Mole is an anthropomorphic mole distinguished by his hat, signifying his membership in a mole-like species. His existence centers entirely around an underground lifestyle. His residence and daily routines are fundamentally adapted to this subterranean environment, presenting a distinct way of life. During the episode "Mole Life," Leonard encounters Naoko Watanabe. His underground existence profoundly inspires her, leading Naoko to contemplate adopting a similar lifestyle herself. This interaction defines his primary narrative role. Leonard belongs to a mole family. Both his father and mother are anthropomorphic moles who wear glasses. His mother also wears hair ribbons, establishing clear family visual traits. Within the series, Leonard is identified as a middle school student.