Footprint
Footprints are the tracks left by a Pokémon. Each Pokémon has a unique footprint that is displayed in the Pokédex of every game since being introduced in Generation II. However, this is only applied to Pokémon with visible legs. Out of the 493 Pokémon in Generation IV, 108 (22%) do not have a footprint.
In the games
When a Pokémon is caught, its footprint is included in the data added to its entry and can be found on the first page. For those without a footprint, the area footprints are displayed on remains blank.
At the start of Pokémon Ruby and Sapphire, a School Kid initially blocks the entrance to Route 102 as he thinks he has found the footprints of a rare Pokémon there. It later turns out that they were his own.
Dr. Footstep on Route 213 in Sinnoh is a footprint expert, and can evaluate a Pokémon's happiness simply by looking at its tracks. He will hand out a ribbon to Pokémon with a high happiness value if they have a footprint.
Wigglytuff's Guild in Pokémon Mystery Dungeon: Explorers of Time and Darkness judges a Pokémon's worth by its footprint. Before being allowed to enter, a Pokémon must stand on a grate in front of the guild entrance and have their footprint identified. At a couple of points during the storyline and at any time after graduating, the player takes part in this sentry duty. It plays out as a mini-game where a series of Pokémon must be identified by their footprints, though more clues are provided over time. The game also notes the Pokémon who lack footprints in the scene where Dusknoir visits the guild.
