When fired, a Proximity Egg will follow gravity and stick to a surface, exploding if someone gets too close to it, much like proximity mines from Rareware's other first-person shooter game, GoldenEye. Clockwork Kazooie Eggs also will trigger the Proximity Egg, so it makes a great alarm system if you are holding up a base in Multiplayer. When firing, Kazooie makes the same sound as she does when firing a Clockwork Kazooie Egg.
Proximity Eggs can also be safely detonated from a distance by shooting them with another egg. Once a Proximity Egg has stuck to a surface, it takes about five seconds to arm itself and become mostly transparent, making it harder to see.
Other players can collect Proximity Eggs by grabbing them before they become fully armed. Shooting someone with a Proximity Egg will simply give it to them and cause no damage (but they will flinch).