Hi! I created this blog post for asking a question that I‘ve been wondering for a long time now. Recently, I found this strange Duplo brick again. I don’t know where I got it from but I already have it for a while now. It is as tall as a Duplo brick and a Duplo 2x4 plate stacked together. Technically, it looks like a normal brick with 4 studs on one side, but on the other side it has a black circle on it. What’s weird too is that it even has a line on the height where the 2x4 plate would be, but it’s one brick. Not removable. See the photos below for more details. If you know where this brick is from, please tell me! Any help is appreciated. Thanks!