It is not uncommon in science that one can gain better understanding of a class of objects by studying its representatives with the extreme properties. In this talk I will describe two types of extreme planetary systems that can help us better understand planet formation in general. First, I will discuss formation of planets in binary stellar systems, which include the circumbinary planets ("Tatooines") recently discovered by the Kepler mission. It is known that planetary genesis in such systems is adversely affected by the perturbations induced by the non-Keplerian potential of the binary. Our group has recently made important advances in understanding the dynamics of planetesimals in such systems by highlighting the (previously overlooked) key role played by the gravity of the protoplanetary disks in which planetesimals grow. I will demonstrate how these developments may help us constrain the theories of planetesimal formation in all kinds of protoplanetary disks. Second, I will describe the connection between the metal enrichment of white dwarfs, observationally inferred for up to 50% of these degenerate objects, and the presence of planetary systems around them. After the brief description of the rich observational phenomenology of these objects I will discuss our recent work on the mechanisms responsible for the transfer of planetary material into the atmospheres of these white dwarfs. Such extreme planetary systems represent unique probes of the bulk composition of the extrasolar minor bodies, inaccessible by other means. They also directly inform us about the statistics of planets around the stars more massive than the Sun, which are difficult to study while the stars are on the main sequence.
Followed by wine and cheese in Pupin 1402.