God dammit Japan...

[A Black Falcon]

To explain it (in part) a bit more, the idea of the joke there is that the rabbit guy likes maids and dresses robot-girl as a maid. Then she does a cat-maid pose and says a standard maid line about 'master'. In Japan there is a definite fanbase for maids, and that generally means maids with French-style outfits. It's not only anime either, there are apparently themed restaurants where the waitresses dress as maids, and, of course, call the customers master. It's kind of weird and problematic but it's a common thing. The very young-looking age of the robot girl makes this creepier than most, but that is the idea. It's not (just) a sexual thing. That scene makes a lot less sense for anyone who doesn't know about Japan's fascination with maids (and, to a slightly lesser extent, [British-style] butlers), certainly.