Agent 3 (Splatoon)

Agent 3 is the role the player assumes in Octo Valley, assigned by Cap'n Cuttlefish.

Appearance
Agent 3 can have a variety of appearances, depending on the player's choice of gender, skin color, and eye color, as well as their current ink color. They wear the Hero Suit, and can pick up Armor to wear as well. They wield the Hero Shot by default, but can use a Charger or Roller for amiibo challenges.

History
Not much is known about Agent 3's background, except that they are at least 14 years old, since they have complete control over their squid and humanoid forms.

Splatoon
Agent 3 initially went to Inkopolis for an unknown reason, but got swept up in Cap'n Cuttlefish's quest to save the Great Zapfish. In Octo Valley, Agent 3 completes various missions to retrieve stolen Zapfish, defeating many Octarians along the way. Eventually, Agent 3 confronts DJ Octavio, rescuing the Great Zapfish, rescuing Cap'n Cuttlefish and restoring Inkopolis' power supply.

Splatoon 2
In Splatoon 2, the role the player takes in single player has been replaced by Agent 4. Agent 3 was mentioned various times throughout the game through dialogue and Sunken Scroll number 25 reveals Cap'n Cuttlefish went off travelling with Agent 3 for some kind of research trip "at the cape".

Octo Expansion
Agent 3 returns in Splatoon 2's Octo Expansion. Agent 3 retains their original Hero Suit, now also wearing a gray torn cape with a number "3" in Inklish which can be seen on other clothes like the Urchins Jersey. When Agent 8 collects 3 of the Thangs, Cap'n Cuttlefish will decide to make a "Missing" poster for Agent 3 which will have the player determine Agent 3's gender, skin color, and eye color.

After Agent 8 collects all four of the Thangs, the Telephone builds it and tricks them and Cap'n Cuttlefish inside to kill them until Agent 3 busts in from the ceiling and destroys the blender, responding to the CQ-80 distress signal. Agent 3 is then rendered unconscious and Cap'n Cuttlefish stays behind to look after them as Agent 8 goes through the hole Agent 3 made. The Telephone then attacks Agent 3 which has them partially sanitized and brainwashed into tying up Cap'n Cuttlefish and attacking Agent 8 before they can leave. After being defeated, Agent 3 is once again unconscious and wakes up after Agent 8 defeats the NILS Statue and Commander Tartar and now has a band-aid on the back of their head on as the staff credits roll. When Agent 8 comes back to the Deepsea Metro, Cap'n Cuttlefish tells them that Agent 3 went back on patrol, explaining their absence. After Agent 8 completes all the tests, a locker in the Central Station will open and Agent 8 will have a flashback to the first time they heard the Calamari Inkantation, prompting a battle with their "inner Agent 3".

Etymology
The name Agent 3 was given by Cap'n Cuttlefish because Agent 1 and Agent 2 are Callie and Marie, respectively. Agent 3's real name is never revealed.

Trivia

 * Although Agent 3 is depicted as female in official artwork, the second Sunken Scroll in and the Splatoon 2 Octo Expansion trailer, the expansion's storyline allows the player to customize Agent 3's eyes, skin tone, and gender using the same options available from, to allow players of the original game a level of personal canon. Their ink color however, remains yellow.
 * After defeating Agent 3 for the second time, you will receive the Golden Toothpick. Funnily enough, it comes with the ability Special Charge Up, possibly referencing the fact that Agent 3 can get specials very quickly.

Splatoon

 * Two sets of Gear identical to Agent 3's outfits can be unlocked for online play.
 * After completing Octo Valley, the player is rewarded the Hero Headset Replica, Hero Jacket Replica, and Hero Runner Replicas.
 * At Levels 25, 30, and 35, Judd will give the player the Armor Helmet Replica, Armor Jacket Replica, and Armor Boot Replicas, respectively.

Splatoon 2

 * The Hero Headset Replica, Hero Jacket Replica, and Hero Runner Replicas are now rewarded by the Callie amiibo, and the Armor Helmet Replica, Armor Jacket Replica, and Armor Boot Replicas are now rewarded by the Marie amiibo.
 * In the English translation of Splatoon 2, Marie remarks to Agent 4 that Agent 3 has fairly poor hygiene. Meanwhile in the Japanese version, Marie states that Agent 4 looks just as good as Agent 3.

Octo Expansion

 * When unconscious after Agent 8 defeats them, Agent 8 can cover Agent 3 in ink similar to Cap'n Cuttlefish. The ink covered on them will slowly go away.
 * The options when "creating" Agent 3 are the same as the first game, the most notable example being the eye color choices.

Super Smash Bros. Ultimate

 * One of the customization options for female inklings is the ability to play as Agent 3.