rationalskepticism.org

Isis finds the pieces of his body, except his penis (which is eaten by fish), and puts them back together

This is incidentally also a theme found in Finnish mythology tho in our (official) version, Lemminkäinen is reconstructed completely (and I'm sure he'd killed himself if his penis had been eaten by fish ) and he resurrects in the "normal" world (insofar as the mythical Kaleva is normal).

Anyhow, on the subject itself I'm not entirely sure if the general idea is to make the entire Osiris story parallel to Jesus' but rather to fit out and if necessary to shoehorn the similar details in them to bolster up the case that the mythology surrounding Jesus borrows from other sources