In the flashback scene where Homelander meets Billy, he says, "Love that accent." Antony Starr speaks with an American accent in the show, but both he and Karl Urban hail from New Zealand.
Antony Starr has said that part of his approach to Homelander is to portray him as someone who sees himself as a father figure to the other members of The Seven. Homelander thinks they're like children who require his firm guidance and discipline.
When Hughie's father says "Jings," it's a nod to the Scottish slang exclamation Wee Hughie often says in the comics.
Grace Mallory is an adaptation of Greg Mallory from the comics. In both cases, Mallory was a CIA Case Officer who decided to start investigating superheroes. Mallory recruited Butcher, Mother's Milk and Frenchie to form The Boys long before Hughie ever joins the team.
In the comics, Homelander knows who Billy Butcher and The Boys are from the beginning. It's established early on in the comics that The Boys and The Seven have been in an uneasy armistice for some time.