Woody Harrelson improvised many of Mr. Brunner's quips and jokes, to the delight of writer and director Kelly Fremon Craig.
Hayden Szeto (Erwin) is eleven years older than Hailee Steinfeld (Nadine).
Kelly Fremon Craig sent the original script, then titled "Besties" to James L. Brooks. Brooks agreed to produce the film, but in one of their first meetings, Brooks told her, "The most important thing you have to figure out is what you want to say about life in this story", a piece of advice that would help her refocus the plot and add dramatic elements.
The original script, titled "Besties", centered more on the comedic aspect, and Nadine's friendship with Krista, rather than the friendship being one of the aspects affecting her life. That script did not have Mr. Bruner (Nadine's teacher). Nadine's full name was Nadine Hamidi Yousefa Rostami, her mom's boyfriend was envisioned differently (with dialogue), there wasn't even a mention of her father's death, Nick was Hot Soccer Dan and had around two lines of dialogue, Erwin was a flutist instead of an aspiring filmmaker, and it had a prom sequence at the end.
Nadine wears a t-shirt from The University of Tuktoyaktuk. Tuktoyaktuk is a hamlet of about eight hundred fifty people located on the Arctic Ocean in Canada.