First of all, yes, I'm strange.

Which brings me to the content of this journal.

I was pondering the plural of the platypus, so I decided to delve into the etymology of our furry duck-billed friend.

First off, it turns out that platypus, or better yet, platypous, is a Greek noun. Literally, it translates to "flat-footed". (So why do we use "pig" instead of "platypus" when referring to cops? )

Now, I wasn't able to determine if platypus (I'll use the modern adaptation of the noun, for sake of consistency) is a second- or third-declension masculine noun, so I will present my pluralization arguments for both cases. However, it is more likely to be the same as the Greek third-declension noun octopus, as this word is a very close compound structure as platypus - it literally translates to "eight-footed". One thing I am not sure of is if the original of octopus ends in the same "-pous" as platypus does. This would have a big impact on determining both the pluralization and the declension categorization of platypus.

First case:
Assuming platypus is a second-declension masculine noun, this would mean the plural ending would be "-oi", giving us "platypoi" as the plural. With modern language trends, where many Greek nouns have had the "-ous" truncated to "-us" (despite the "o" actually being part of the root, rather than the ending), we have also truncated the plural ending from "-oi" to merely "-i".
Therefore, this would give us platypi as our (closest possible) correct modern pluralization.

Second case:
Assume platypus is a third-declension masculine noun, liken to octopus. This noun properly pluralizes by becoming octopudes. Since this seems awkward in modern English, the proper variation of this pluralization has been accepted as octopuses.
Therefore, this would give platypudes as the correct pluralization, with platypuses as the modern result.

Basically, this means the argument boils down to which declension the noun falls under. Until that is determined, either form is equally acceptable and correct.

I offer a third option, based upon third-declension status.
Call them platypods.