The tag alias #63210 cock_parasite -> parasitic_penis is pending approval.

Reason: Most things tagged with the former are also tagged with the latter, implying that most users (or at least the ones that do the tagging) consider them to be synonymous, or nearly so.

Alternatively, separate wiki pages could be created for both. The definition of 'cock parasite' could be something along the lines of "a parasite that infects the penis", while the definition for 'parasitic penis' could be something along the lines of "a parasite that has replaced or merged with a host's penis".