A number of weapons (e.g. Stray Asteroid) and other cards (e.g. Fingercuffs) affect adjacent bunnies, i.e. bunnies that are next to each other in the Bunny Circle regardless of ownership. Quite Irascible Diffractable Cheese Balls, while it is a ranged weapon, does not actually affect bunnies adjacent to the initial target.
A Barrier or Neutronium Barrier blocks the effects of a ranged weapon, reverses (or destroys) a Roaming Red Run, and prevents Fingercuffs from being applied to bunnies on each side, thus the two bunnies immediately next to any barrier are not considered adjacent. Barriers must be placed between two adjacent players, and can not be placed between two bunnies owned by the same player.
Some cards (e.g. Melding) require interactions between adjacent players, usually involving passing cards to the next player clockwise or counter-clockwise.