Platypi or platypuses?

The plural of "platypus" has long been established in the English-speaking world as "platypuses." This is due to the Greek root of the name ("flat-foot"). The actual Greek plural for "platypus" is "platypodes," but this isn't used in English. "Platypuses" is the accepted plural form because it aligns with the regular pluralization rules for words of Greek origin and is endorsed by authoritative language sources such as the Oxford English Dictionary and Merriam-Webster.

As for “platypi”? Well, English is an evolving language, and common usage sometimes dictates a word's acceptance. So, using "platypi" may be a fun and quirky informal term, but strictly speaking, it's not considered correct by most authorities on English usage, including major dictionaries and linguistic guides.