An ancient mechanism that was traditionally used as an ellipsograph (a device used to draw ellipses). In recent times these have been sold as toys or novelty items often labeled as 'Do Nothing Machines', which is a bit of a misnomer as they can serve a purpose.

They are kind of fun to play with and this is just one of many ways to build one out of LEGO pieces.

Kristal used this mechanism to achieve the motion of her skating penguin in the referenced video.