Phenotypic plasticity, or the ability of a single genotype to produce multiple phenotypes, has recently gained the attention of not only evolutionary biologists, but also of ecologists and behaviorists. Molluscs have proven to be an important system for studies of plasticity, and molluscs now provide us with some of the best examples of inducible offenses, defenses, flexible life histories as well as community wide ecological impacts termed trait mediated interactions and indirect interactions. Studies on molluscs are often justified because, due to the extensive fossil record of many molluscan groups, current studies can give us insight into both patterns and processes that were historically important. I examine the types of plasticity that have been studied in molluscs, believed ecological and evolutionary implications and consequences of these plasticities, and where we should look for additional plasticities that have yet to be studied. I consider which of these types of plasticities could be detectable in the fossil record, and if there are processes that could be inferred from known plasticities that might be preserved in fossil assemblages.