A hidden easter egg that changes the logo of the DuckDuckGo website if you search for hatsune miku. The website DaxDuckDex tracks which ones have been found so far. There are a lot of them.
There was a rumor that these were AI-generated. Seems believable since at this time there are several hundred of them and there are clear errors in many of these. Zundamon, for example, looks like it's just green Miku with a suit.
However, the creator claims they do use AI in the process but most of it is manual:
The design process does involve AI, but it is still a fairly manual process, and our design team (and others) have been involved in it.
AI helps but it’s a slow, human-driven process that mainly I do right now. I get some things wrong for sure but also I can fix them and the aliases. Should have updates on Monday but let me know what I need to fix.