A multi-purpose subterranean digger as well as a helicopter, the Slug Digger is used to burrow down underground into the Invaders' base. Three large cranes holding them are found near the end of an excavated cave; one of them was already taken when the heroes arrive.
The Slug Digger has retractable drills on the left, right, and bottom sides which are used to drill into the earth and sports two Vulcan cannons that can also tear down the dirt with its bullets. Its cannon shot is a mine that stays in place until an enemy touches it or it is shot.
Due to being several meters underground, the players cannot get out of the Slug, nor can they perform the Metal Slug Attack with it. If the Slug Digger is destroyed, the player is killed, and they respawn from above in a new Slug Digger.
In Other Games
The Slug Digger appears in Metal Slug Attack representing the Rank Match submode.
It later appeared as a playable unit in the form of the Digger Base, which utilizes the cranes from Metal Slug 6. The Digger Base is built by a Miner, with each base launching up to three Slug Diggers towards the enemy; two that relentlessly move forward while drilling away at the enemy, while another tracks them from above. Both the base and the Slugs themselves are resistant towards explosive and incendiary attacks and are equipped with self-repair technology.
- The Slug Digger's Japanese name, Mister Slug, and the final mission's second section is a reference to the Mr. Driller series.
- "Slugs". Action Gameside: Vol. 3, Nov. 2013, pg 53. http://6th-divisions-den.com/archives/ms6/Action%20Gameside%20N%C2%B03/Scans/AG%20Page%2052-53.jpeg
- Metal Slug Attack. Digger Base description.