Approval of God: Despite receiving an executive producer credit, Dav Pilkey was decidedly hands-off with the production and only gave direct approval of the first draft of the script. In his words, he wanted to "experience Captain Underpants as a fan" (not to mention he didn't want to call the shots in a medium he had no experience in). He would go on to give the movie glowing praise◊, particularly to Mr. Krupp's Character Development.
Billing Displacement: Thomas Middleditch is credited fourth despite fellow lead actor Kevin Hart being credited first. This is extra strange not only due to crediting Middleditch strangely late for a main protagonist, but also because he is not billed directly next to the other protagonist.
Dawson Casting: George, Harold, and Melvin are all voiced by adults.
Dub Name Change: This caused the film's release to be postponed in Spanish-speaking Latin America. In early trailers, the character names are left in English (except Captain Underpants). In the movie itself, the Spanish book translations are used after DreamWorks received complaints from fans.
Dueling Movies: Captain Underpants was set to go up against Wonder Woman (2017), a "real" superhero movie, on the same day. Regardless, both films did well in terms of reception and several moviegoers have jokingly combined the two into "Captain Wonderpants."
Fake American: Thomas Middleditch, who is Canadian, voices Harold, who lives in Ohio.
Fandom Nod: In the Flip-O-Rama segment, Harold accidentally rips the paper after flipping the pages too quickly. This was based off of many readers reporting themselves doing this same thing.
Milestone Celebration: The film was released very close to the twentieth anniversary of the first book's publication.
No Budget: The film had a budget of $38 million, which is generally pretty low for an animated movie. It's especially low for a major studio like DreamWorks, making it their second cheapest film after Wallace & Gromit: The Curse of the Were-Rabbit. This is lampshaded by George and Harold when they mention showing the film's final battle would make it go overbudget, so they present it in Flip-O-Rama instead. It's also why most of the cast from the book are Adapted Out in favor of only five main speaking roles.
Saved from Development Hell: The film had been in development since 2012—the release date had been relocated a couple of times, Rob Letterman stepping down as director with David Soren replacing him, and DreamWorks' issues in the last few years probably haven't helped. Thankfully, the film was finally released on June 2, 2017, and most agree that you can't even tell watching it that there was any sort of troubled production.
So My Kids Can Watch: Kevin Hart has stated that his son being a fan of the book series is one of the factors that drew him into voicing for the film.
Stillborn Franchise: The film is called the "First Epic Movie", but there doesn't seem to be any plans for another epic (i.e. theatrical) movie. However it did help spawn a Netflix series.
◊, particularly to Mr. Krupp's Character Development.
