I remember them being fairly popular when I was in reception class, so around 2009. They were figurines of what appeared to be either aliens or robots, possibly some were aliens and others were robots. By 2011, the trend seemed to have died down as I don't recall them ever being mentioned since then. Around that time my older cousin also unloaded his collection on me (I didn't have any before then) and even though they didn't seem to be as big by that time I still felt like hot shit for having them (a kid in my class brought one into school around then so the trend wasn't completely dead).