Evolutionary relationships among complex, multicellular eukaryotes are generally interpreted within the framework of molecular sequence-based phylogenies that suggest green plants and animals are only distantly related on the eukaryotic tree. However, important anomalies have been reported in phylogenomic analyses, including several that relate specifically to green plant evolution. In addition, plants and animals share molecular, biochemical and genome-level features that suggest a relatively close relationship between the two groups. This article explores the impacts of plastid endosymbioses on nuclear genomes, how they can explain incongruent phylogenetic signals in molecular data sets and reconcile conflicts among different sources of comparative data. Specifically, I argue that the large influx of plastid DNA into plant and algal nuclear genomes has resulted in tree-building artifacts that obscure a relatively close evolutionary relationship between green plants and animals.