Mipsey and Pipsey are different shades of purple and have white eyes and wear black collars. They appear to be larger than normal worms. However, in reality, they are smaller and thinner.
Mipsey and Pipsey were borrowed by SpongeBob in order to catch Patrick and take him to the dentist. They managed to corner Patrick to a coral tree and were immediately called off by their owner, an Old Lady who still has her baby teeth.
They are referred to as "Blood worms" in the end credits of "The Whole Tooth."