  We examine finite temperature perturbation theory for Chern-Simons theories,
in the context of an analogue 0+1-dimensional model. In particular, we show how
nonextensive terms arise in the perturbative finite temperature effective
action, using both the real-time and imaginary-time formalisms. We illustrate
how large gauge invariance is restored at all orders, despite being broken at
any given order in perturbation theory. We discuss which aspects generalize to
a perturbative analysis of finite temperature Chern-Simons terms in higher
dimensions.
