animalese.js is a JavaScript library that synthesizes an approximation of the villager speech sounds from Animal Crossing.
At 40% (closer to Grump than Isabelle) it reads Spanish quite well. I'm not sure it's intentional.
Japanese and Spanish happen to have very similar pronounciation. It's a neat detail in the Animal Crossing games that seems to have gotten mostly lost in translation for the English version.
From a quick glance, it's a very simply a premade wav file which has all letters A to Z with 0.15s for each. The final wav is just a concatenation of all of letters from the text, and a silence of each unknown character/space. It doesn't support numbers but could easily be extended beyond what's in the demo. Very clever.
What and why is this?
In Animal Crossing, the characters' audible speech seems like it's speaking the first syllable or two of each word in the text dialog and sped up, and the pitch control varies between characters, so while it generates amusing gibberish, some of it is lightly comprehensible and interesting and OP's link is a pretty good replica of it.