Big Run

Big Run is a special event in Splatoon 3. They were first announced to occur in the Splatoon 3 Nintendo Direct. Big Runs are limited-time events in which Salmonids invade the stages used by Inklings and Octolings for Turf War and Anarchy Battles, allowing players to partake in Salmon Run Next Wave on those stages.

Description
In the initial announcement, footage of a Big Run shift at Wahoo World interrupted the previously shown Cohozuna footage with glitch-like effects. In what was shown, Boss and Lesser Salmonids attacked a player attempting to collect and place Golden Eggs in an Egg Basket atop the center platform of the course. All sections of the stage except the central platform and the standard spawn point areas of the map were flooded, and the sky was red. This event was said to occur every few months. The trailer also features a remix of Clickbait in the style of ω-3.

At the end of the Chill Season 2022 announcement trailer another Big Run trailer interrupted the shown footage, showing off more of what Big Run taking place at that stage would be like, as well as Splatsville's cosmetic changes throughout the event. The trailer starts showing what seems to be a snippet of the Big Run Splatcast, and then shows Splatsville with a pink sky and helicopters overhead, while there are new posters stuck all around inside and outside Grizzco. During Wahoo World Big Run gameplay, the sky in-stage is now a dark pink, and Grizzco helicopters are flying overhead. The stage remains unchanged from the first trailer, though more of it is shown, with the three different tides, Known Occurrences and Xtrawaves being confirmed to be in Big Runs.

Big Run is described as "a phenomenon where mass numbers of Salmonids swim upstream once every few months" in the 2.0.0 patch notes. Big Run will be accessible through the Grizzco building during the event period, restricting access to regular Salmon Run shifts, similar to how Splatfest Battles restrict access to non-Splatfest Turf War battles and Anarchy Battles. Normal battles will still be available, but the current Big Run stage will not available till the event is over.

Rewards
At the end of each Big Run event, exclusive locker decorations are awarded based on the highest team-wide Golden Egg total the player achieved in any one shift. This score is ranked relative to the high scores of all participating players, with different decorations awarded to players whose high score is in the top 5%, top 20%, or top 50% of scores. Players not in the top 50% still receive a basic version of the decoration. 

Badges
Badges are available for reaching each tier of high score in any Big Run event.

Quotes
""Big Run" is a phenomenon where salmon rushes to the area where the squid live. It is rumored that it occurs once every few months. During the big run, the stage you usually use in battle will be the stage of your part-time job."

- Splatoon JP, Twitter

Trivia

 * During the initial Big Run reveal, the sky in the footage was a dark red, matching that of the sky when an Xtrawave is happening outside of a Big Run. This was most likely a placeholder, as the sky was changed to pink in the second trailer.
 * In the background of Wahoo World, the "seven rings" mentioned in Splatoon 2's Sunken Scroll 17 can be seen.
 * The Sunken Scroll's illustration also appears briefly in the Chill Season 2022 announcement trailer for a few frames at the beginning of the Big Run segment.
 * Players do not have to reach Level 4 to participate in Big Run, unlike normal Salmon Run. This is seen in the stage schedule in SplatNet 3, where it shows a banner reading, "Big Run happening now! Grizzco hiring ANYONE!"
 * In this mode, it's revealed that Salmonids hide in Gushers before a wave starts.