The Big Build Marathon was an event held on Friday June 29th, 2018. Running at four hours, it marked the world premieres of a brand-new Thomas - The Trainz Adventures episode, the half-hour Mainland Presents: Railway Escapades special, and Thomas the Building Engine.
- 5:00pm - Trainz Time With TheGermanOfSodor
- 5:30pm - Thomas - The Trainz Adventures: "Two Left Buffers (world premiere)/Lazy Dennis"
- 6:00pm - Enterprising Engines: "Blunderbuss/Snow Problem"
- 6:30pm - Story Stops with Carson marathon
- 7:30pm - Mainland's Railway Escapades (World Premiere Special)
- 8:00pm - Tillie to the Rescue/Casey Jr's Mail Run
- 9:00pm - Thomas the Building Engine (World Premiere)
- Technically, the marathon marked several firsts for The MilanToon Channel:
- The first marathon to feature world premieres outside of the channel.
- The first to utilize customized screen bugs for each block.
- The first marathon to exceed the usual two-and-a-half-hour limit.
- The marathon was originally planned to be entitled The On the Road Marathon (with the lead-up to Thomas the Building Engine being all four preceding Crotoonia's On the Road videos), but was scrapped when the event was cancelled.
- The marathon branding and bumpers were loosely inspired by The Super Spongey Square Games (a one-hour SpongeBob Squarepants premiere event) and The Lost Eds' Marathon (a marathon leading up to a "lost" episode of Ed, Edd, 'n Eddy).
- This is the highest viewed marathon/stream on the channel to date, with a record 203 peak in viewership during its live broadcast.