AbstractOne may argue that, today, proceedings articles are not useful. Results belong in refereed papers and even reviews are best in publications that are long enough to do justice to the topic reviewed. In this short review, reflecting a presentation that was given at the IAU343 symposium, Why Galaxies Care about AGB Stars, I have therefore endeavoured to include some practical snippets that, while remaining true to the presentation, also provide a quick look up reference. After a reminder of how few AGB stars actually interact with a companion, and a pictorial summary of the types of interactions that can happen, I list the rapidly growing body of 3D common envelope simulations. Next, I highlight shortfalls and successes of simulations, and then spend some time comparing the two simulations of planetary nebulae from common envelope interactions to date. Finally, I summarise a handful of results pertaining to common envelope interactions between giants and planets.