As part of their usual idol costumes (as shown in my last post), the members of Niconico☆Alienz wear small star-shaped markings made from usually either stickers or temporary tattoos; going with of their theme of being "weird" compared to others around them, the placements of these stars are meant to highlight what makes them weird, even though a lot of them cannot be seen in their usual costumes (or in general, such as the ones on the chest and stomach).
🍬 Emu: the corners of her mouth, her elbows, and her knees - the parts of the body that move when doing a wonderhoy.
🎹 Saki: parts of the body impacted by her chronic illness - her nose, mouth, throat, and chest for respiratory illnesses, her stomach for lack of appetite, and her legs for general weakness.
🐹 Kohane: similar to Saki, areas meant to symbolize her social anxiety - the forehead for her mind, the eyes for tears and lack of eye contact, the mouth and throat for trouble speaking, and the heart for elevated heart rate.
🎀 Mizuki: unlike the others, her star placements aren't for any specific body part, but rather places where they could be easily hidden - behind bangs, shirt collars, sleeves, socks, skirts, all with stars barely peeking out. While she of course has not told them the specifics, when discussing what makes them each different, Mizuki simply mentioned that there are a lot of things about herself that she has to keep secret, and thus this idea came to be. In addition, she typically adjusts where on her body the stars are, since what one outfit hides another doesn't.