It is now widely known that a spectator field (or a light scalar field) can generate primordial density fluctuations such as in the curvaton mechanism, modulated reheating model and so on. First I will talk about the current status of such spectator field models. Then I will also discuss a model with a spectator field where a large tensor-to-scalar ratio can be realized even in small field inflation models. A generalized version of the so-called Lyth bound which includes a spectator field is also presented.