Seán and Mark are famous YouTube gamers. They have collaborated several times. Their first video together was a gmod sandbox video that was released on April 24, 2014.
Mark once did a video where he took quizzes on how we he knew jacksepticeye. In this video, Mark intentionally answered incorrectly on the question asking about Mark and Seán's ship name. He got scores of around 70-80% on each quiz.
On July 28, 2017, Markiplier uploaded the video DARKIPLIER vs ANTISEPTICEYE, which is a collaboration between multiple YouTubers, featuring their evil counterparts. Seán and Mark appear in the most notable roles in the video.
In 2018, Seán and Mark teamed up to create the clothing brand CLOAK. Both of them published videos announcing it at the same time. Seán has also promoted CLOAK on his Twitter.
Septiplier is a very popular ship within the YouTube community, one of YouTube's "power couples." On AO3, it's the second most written romantic ship and third in total within the Video Blogging RPF (YouTube) tag; Mark's most written, as well as Seán's most written. Fanart of the two is also popular.
Seán and Mark were featured in the video We're sinking bois by Reddit user mrbananoid2, which has characters from the movie Titanic edited to be PewDiePie's most famous supporters. Seán and Mark appeared to be a couple in this video, as they were closely together in a bed and held hands.
- Septiplier tag on Deviant Art
- MARKIPLIERANDJACKSEPTICEYE tag on Deviant Art
- Septiplier-Fans fanclub on Deviant Art
- Danti refers to the ship between Seán and Mark's evil alter egos: Darkiplier and Antisepticeye
- Seán himself has shared his thoughts on Septiplier, stating that while he enjoyed the fanart of him and Mark hanging out as friends, some people took the ship way too far with more inappropriate fanart and fanfictions.
- After this event happening, Seán and Mark did not like the ship.
- Seán and Mark's ship name is a mashup of their gamertags: jacksepticeye/Markiplier (Septiplier).
- Seán and Mark are associated with a color; Seán is green, while Mark is red.
- As of 2015, Seán's favorite color was red, while Mark's was green.
- Some fans refer to them as "green PewDiePie" and "red PewDiePie", as the two are often associated with the more famous YouTuber PewDiePie as well.
- Both dyed their hair to their signature colors at some point.
- Both Seán and Mark did live streams where they told people to subscribe to PewDiePie when the subscriber gap between him and T-Series had reached an all-time low on separate occasions. These live streams were similar in style.
- The two follow each other on Twitter.