Inkling Girl with the Smash symbol in her eye, as seen during Ultimate's first teaser trailer.
Although not released on the Smash website like the Super Smash Bros. for Nintendo 3DS and Wii U character posters, this was posted on the official Japanese Splatoon Twitter account in celebration and seems to fill the same role. It was posted on December 6th, 2018, 1 day prior to Ultimate's official release.
Inkling's Congratulations screen, with the Squid Sisters and Judd.