MatPat

Pursuing his dream of becoming an actor, Matthew moved to New York City after graduating and performed in theater productions to little success, spending two years unemployed.[6]^{: 04:20–06:15} His first YouTube videos were auditions for stage plays. In 2011, he decided to revamp his channel as a "portfolio" which could demonstrate to potential employers his ability to write, research, and edit videos online.[8] Inspired by an Extra Credits episode on tangential learning,[7] Patrick uploaded the first episode of "Game Theory" on April 18, 2011.[9] It discussed the quantum mechanics in the 1995 video game Chrono Trigger.[8]

The channel slowly gained subscribers and his videos were posted on the front pages of sites such as ScrewAttack and GameTrailers.[10] In 2012, Matthew introduced two new segments hosted by fellow YouTubers Gaijin Goombah and Ronnie Edwards, and Austin Hourigan's "The SCIENCE!".[11] In 2014, Matthew launched the spin-off channel "Film Theory", which covers movies and television.[9] This channel reached over one million subscribers in a month.[12]

He occasionally uploaded videos commenting on the gaming market and gamers, as well as on other matters that he deemed noteworthy.[13]

Patrick with his wife Stephanie in 2018

Matthew started a Let's Play series called GTLive on August 26, 2015,[14] where he posts gameplay and video reactions with his wife Stephanie. Starting on October 3, 2016, the Monday streams became part of YouTube Gaming Primetime, and were therefore scheduled for 3 pm to 5 pm PST. It also included a voting mechanism, which can be used by Matthew to conduct quick polls.[15] As of March 2022, GTLive had 2.94 million subscribers and over 649 million views. As of 2022, the GTLive channel continues to upload mostly unedited, pre-recorded content.

On June 8, 2016, Matthew posted via his YouTube channel a new show, MatPat's Game Lab, on Google's paid subscription service, YouTube Premium. The show mainly focused on placing video game players in real life scenarios mimicking scenarios that occur in video games, such as bomb defusing, parkour, survival and military training.[16][17] Despite MatPat's interest in developing a second season, YouTube did not announce any further development into the project.[18] He was also a part of the YouTube Premium series Scare PewDiePie (2016),[19] created by PewDiePie, and the third season of Escape the Night (2018), created by Joey Graceffa, in addition to cameo appearances in Markiplier's YouTube Original films A Heist with Markiplier(2019) and In Space with Markiplier (2022).

On May 29, 2016, Matthew and eleven other YouTubers met with Pope Francis for an hour. Patrick asked the Pope to encourage others to "fight for what's right" and gifted him a copy of Undertale (2015), saying that its recurrent theme of mercy fits the Pope's proclamation that 2016 would be the "year of mercy for the Catholic church".[20][21]

In 2019, The Game Theorists held a 9-hour charity livestream that generated $1.3 million for St. Jude Children's Research Hospital.[22] The stream included guests Markiplier, TheOdd1sOut, Rosanna Pansino, Scott Cawthon, and others.[22] Two other charity streams were held for St. Jude in 2020 and 2021, respectively.[23][24]

The third Theory channel, and fourth overall; The Food Theorists, began releasing videos in July 2020. The Food Theorists, using the same style as its predecessors, blends food science with psychology, physiology, and conspiracy.[25] The channel was being developed for two years prior to its launch.[26] As of October 2022, The Food Theorists had 4 million subscribers and over 499 million views. It had reached 1 million subscribers exactly a week after launch, and had then gained another million over the succeeding 4 months.[27]

On December 20, 2022, a fourth Theory channel, and fifth overall, was announced[28] on the Game Theory channel, along with the channel's purchase by Lunar X. On February 18, 2023, The Style Theorists was launched. Like the other channels, it focuses on the science, math, history, psychology, and mystery of fashion. It reached a million subscribers three days later.

Patrick also made cameo appearances in multiple installments of YouTube Rewind.

On August 26, 2023, MatPat hosted the Streamy Awards.

Patrick was involved in the web series Terrain of Magical Expertise. He gained the series more attention and exposure by uploading a re-mastered version of the first episode on the channel on October 1, 2013, and then providing a platform for the series.[29][30] Patrick, alongside Cordato, Sundman, Hourigan and Edwards, also contributed their likeness and voices for self-parodied opponents in the video game adaptation. The game was released on Steam on September 9, 2021.

A character based on Patrick was included in The Walking Dead: Road to Survival (2015).[31] In 2017, Patrick and his wife Stephanie participated in Nintendo's Pokkén Tournament DX Invitational, an event held during E3 2017. He was paired with Allister Singh, the only pro-Pokkén Tournament player in the event. His team eventually won the tournament.[32] Patrick voiced Computron in the animated series Transformers: Titans Return (2017).[33]

In 2016, Patrick hosted the go90 reality series The Runner.[34] In 2019, Patrick partnered with Nickelodeon to make the show Fact or Nicktion.[35] In this show, Patrick examined various phenomena in Nickelodeon shows, such as SpongeBob SquarePants, Avatar: The Last Airbender and Rugrats to determine whether they could or couldn't happen in real life.

Patrick is a co-producer of the Broadway play Grey House.[36]

Patrick's videos about the video game series Five Nights at Freddy's have made him prominent within the fandom, which is known for its dedication to theorizing about the underlying narrative of the series.[37]