  It seems to be generally accepted that apparently anomalous cosmological
observations, such as accelerating expansion, etc., necessarily are
inconsistent with standard general relativity and standard matter sources.
Following the suggestions of S{\l}adkowski, we point out that in addition to
exotic theories and exotic matter there is another possibility. We refer to
exotic differential structures on ${\mathbb R}^4$ which could be the source of
the observed anomalies without changing the Einstein equations or introducing
strange forms of matter.
