Hawkeye uses an arrow labeled Pym to grow another arrow to gigantic proportions. In the comics, for a while Hawkeye gave up being an archer to become Goliath. He drank Pym's formula to change size.
Darnell Besaw (young Maya Lopez) and Alaqua Cox (Maya Lopez/Echo) are cousins in real life. While Alaqua is deaf, Darnell isn't, but she learned ASL for the show.
A substantial excerpt of the car chase scene was previewed in Marvel Studios' 2021 Disney+ Day Special (2021). At the start, when Clint and Kate are arguing about which one of them will do the driving, at one point Kate's dialogue is muffled to indicate Clint's hearing problem. In the preview version, this dialogue was audible and her words are: "No, you... you drive, I shoot."
When Kate draws a new costume for Clint, it's his original purple costume, worn when he first appeared as a villain for Iron-Man in "Tales of Suspense." Kate also mentions a hood, which might be a wink at Green Arrow (DC's archer, preceding Hawkeye by decades), or it may be an allusion to the Ronin suit (as a way of inducing Clint to spill more information about Ronin's true identity).
In the comics, Maya Lopez was first introduced in Daredevil #9, Dec. 1999. Her father was killed by Wilson Fisk in the comics, rather than Ronin as shown here. She is raised by Fisk who honors his promise to her father, which is not shown in the episode.