Theseus and Pirithous swore oaths on their friendship, entering into a formal bond like heterosexual marriage. One of the oldest ways of taking this oath was to place their hands upon each other's testicles, the origin of the terms "testify" and "testimony".

Another method of swearing friendship, (becoming blood brothers) was wrestling, followed by pressing together two thumbs which have been cut with a knife.

Hercules attempted to free them from the rock to which they had been bound together in the underworld but succeeded in freeing only Theseus, and left behind his buttocks attached to the rocks. Theseus was referred to as hypolispos, meaning "with hinder parts rubbed smooth."