When opening the local files of the game, go to the "game" folder and then to the "images" folder. There, you’ll find a PDF. Upon opening the PDF, the text "green ogre can’t be saved" can be seen at the top. However, if you select all the text by pressing Ctrl + A, you’ll notice some invisible text at the end of the page, in the same color as the PDF background:

don(key):
"no matter what"

By entering "no matter what" as the donkey code, an emotional message is spoken by the donkey. But in one of the texts, the message turns purple. Clicking on it sends you to a link. On this link, a large file opens, and once again the message "green ogre can't be saved" can be seen. However, if you scroll all the way down the page, there's another message:
"but you can try pausing and listening closely to his breathing next time."
I think there might be more secrets hidden in this game that’s considered silly, but for now, that’s all we’ve got about the donkey code.