There’s actually quite a few references to Droids in the prequel films;
FROM BOONTA TO BAOBAB: DROIDS AND THE STAR WARS PREQUELS
https://www.starwars.com/news/from-boonta-to-baobab-droids-and-the-star-wars-prequels
The Boonta Eve is the most blatant reference (by Lucas presumably), while the rest seems to mostly be the concept artists on the PT either intentionally or unintentionally borrowing ideas from the cartoon.