I was trying to ask ChatGPT some advice on how to engineer my prompts (maybe its futile, but nevermind, that is not the point), hit 'enter' and noticed that the response mentioned GPT-3.5 [1]. When trying to dig deeper ChatGPT wrote that <<I mentioned "GPT-3.5" based on the phrasing used in your initial question, but it appears that there may have been a misunderstanding or a mix-up in terminology.>> In a "fresh" chat, any knowledge of GPT-3.5 is denied [2].

Maybe every once in a while, GPT gets fed with wikipedia? Maybe the ".5" came out at random? (actually just the "." token was random and the "5" followed) Is this considered an hallucination?

[1] https://chat.openai.com/share/630926a7-388d-4762-8ee2-6bce24b1c7e3 (note that i missed a final 'is' in my question)

[2] https://chat.openai.com/share/f9b9e6c1-89db-4295-83c4-af12972c3ef1

[3] https://en.wikipedia.org/wiki/GPT-3#GPT-3.5