The Tardicaca Shark, is a fictional fresh water shark species, which is found in Lake Tardicaca. The Tardicaca Shark only appeared in the episode "Crippled Summer", where it was seen having intercourse with Nathan twice. The incident is frequently brought up by Mimsy, much to Nathan's fury.
The shark's shape and size appears is similar to a Great White shark. They share the same shaped fins and head, as well as teeth and eyes. However, it has brown/green skin and nasial barbels similar to those of a catfish. It purportedly has a 9 inch penis, much to Nathan's chagrin.