Mamoru Hosodacompleted all 500 pages of storyboards for the film at Denny's, working in hugely long 12 and 16-hour shifts.
Warner Brothers originally considered localizing the film themselves before licensing it off to FUNimation Entertainment.
The grandmother's birthday, August 1st, is a clear reference to Odaiba Day, a holiday celebrated within the Digimon fandom that is recognized and acknowledged by many Digimon media producers. The director to Summer Wars, Mamoru Hosada, has a history with working on and directing Digimon media, most notably a movie he directed, "Digimon Adventure: Our War Game" (localized theatrically outside of Japan as "Digimon: The Movie" ) which shares a very similar art style, themes, and plot points to Summer Wars.
Ryunosuke Kamiki voices Kenji in the original Japanese dub while Michael Sinterniklaas voices him in the English dub. Later on in the film Your Name, Kamiki would voice Taki in the original Japanese dub and Sinterniklaas would voice him in the English dub.