An input-oblivious proof system is a proof system in which the proof does not depend on the claim being proved. Input-oblivious versions of NP and MA were introduced in passing by Fortnow, Santhanam, and Williams (CCC 2009), who also showed that those classes are related to questions on circuit complexity. In this note we wish to highlight the notion of input-oblivious proof systems, and initiate a more systematic study of them. We begin by describing in detail the results of Fortnow et al., and discussing their connection to circuit complexity. We then extend the study to inputoblivious versions of IP, PCP, and ZK, and present few preliminary results regarding those versions.