a calabi-yau algebra is a noncommutative analogue of the coordinate ring of a calabi-yau variety. it is well-known that if $g$ is a group acting on a calabi-yau algebra $a$, then the smash product $a \#g$ remains calabi-yau under sufficiently good conditions. however, there are cases in which a smash product $a \# g$ may become calabi-yau even if $a$ is not calabi-yau. we will explain how this can occur by studying the more general notion of a \emph{skew calabi-yau algebra}. this is joint work with d.~rogalski and j.j.~zhang.