The series is set on a gigantic, mysterious and seemingly endless train traveling through a barren landscape, whose cars contain a variety of bizarre, fantastical, and impossible environments.

[6][7] All four seasons of Infinity Train have received critical acclaim for their complex themes and characters, writing, uniqueness, visual animation style, and voice acting.

Their travels with a young girl named Hazel and her gorilla friend, Tuba, make Grace more sympathetic to the train's denizens.

After Simon kills Tuba, it is revealed that Hazel herself is one of Amelia's creations, and Grace realizes what she thought she knew about the train is wrong.

Set decades earlier, during the period while Amelia is establishing control over the train, the fourth season centers on Ryan and Min-Gi, two best friends who want to become famous musicians.

Ryan and Min-Gi come to realize that they need each other in order for them to move forward in life, while Kez finally apologizes to the train denizens she harmed.

From October 18, 2019, a series of ten shorts titled "The Train Documentaries" was uploaded onto the Cartoon Network app and YouTube channel.

Guest voices for Book Two include Wayne Knight, Laraine Newman, Nea Marshall Kudi, Bill Corbett, and Rhys Darby.

Guest voices for Book Three include Rhys Darby, Edi Patterson, Phil LaMarr, and Alfred Molina.

[16] He also cites Doctor Who, Agatha Christie, The NeverEnding Story, The Matrix, Philip K. Dick, Star Trek: Voyager, Sliders, and "The Mysterious Stranger" segment from The Adventures of Mark Twain as influences, along with novels such as Nightbirds on Nantucket and The Wolves of Willoughby Chase.

[17][18] Dennis has also described Infinity Train as "Saw for kids," in that each season is essentially a morality play based around machinery designed to help one overcome personal issues and appreciate life.

[19] Infinity Train has three staff writers, who make up the main story team in addition to showrunner Dennis and supervising producer/director Maddie Queripel.

Cole Sanchez served on the story team for Book 1's development but departed to work as supervising producer on Summer Camp Island.

[23] On March 11, 2018, Cartoon Network's official website launched a teaser for Infinity Train that confirmed the pilot had been greenlit as a full series and would premiere in 2019.

"[21] When asked what he would like to do with the series in the future, Dennis expressed interest in exploring other time periods of the train, as well as a movie following Amelia's story.

[7] Dennis clarified on Twitter that he did not intend for it to be the final season, and remains open to continuing the show in the future if given the opportunity.

[43][44] On May 8, 2021, Dennis released a mockup frame from the unproduced Book 5 in response to a fan movement to renew the show trending #1 worldwide and in multiple regions on Twitter.

[45] Gallery Nucleus in Alhambra, California, held an official Infinity Train art show from September 25 to October 3, 2021.

[12] Following its removal from HBO Max, Infinity Train trended on Twitter as fans expressed their frustration and disappointment.

[54] On December 6, 2019, Infinity Train: Book 1 (Original Soundtrack) was released with 27 songs from the first season, including extended versions of "Running Away" and "Boogie Bash (The Monster Party Car)".

"[64] Reuben Baron of CBR favorably compared it to Cartoon Network's animated miniseries Over the Garden Wall in its perfection, hailing it as "a beautifully handled piece of self-contained, character-driven storytelling.

"[65] Skyler Johnson from Comic Watch called it "excellent", with "emotional depth that is rarely seen in children's television", "witty, clever humor", and "stellar voice action.

"[68] Petrana Radulovic from Polygon praised the series' complex character arcs and noted the third season is a testament to the infinite potential of the premise.

"[72] The fourth and final season of Infinity Train also received positive notice, though reception was considerably subdued compared to Book 3.

[74] As the show first entered production, the pilot for Infinity Train was first aired on Cartoon Network on Saturday February 11, 2017, at 6:00 am without any advertisements for it.

[75] Despite this, the pilot pulled in approximately 703,000 views amongst the 18–49 year old demographic and ranked as the 33rd of the top 50 original cable telecasts for February 11, 2017.

[77] In December 2020, Observer Media reported that Infinity Train was the fourth most-watched original series on HBO Max since its launch in May.