In one scene, John Lithgow's character complains to his wife, portrayed by Melinda Dillon, that as a boy when he asked for artist's paints for Christmas that his dad gave him a BB gun. This is clearly a send off to 1983's A Christmas Story (1983), where the lead character Ralphie's quest was to receive a BB gun for Christmas. Melinda Dillon played Ralphie's mom. Though there is no proof of this and its just coincidence.
According to cryptozoologist Loren Coleman, some characters in the film are based to varying degrees on actual figures in the search for Sasquatch. "Jacques LaFleur" (David Suchet) is a nod to the late Canadian Rene Dahinden, and "Dr. Wallace Wrightwood" (Don Ameche) combines some qualities of John Green, Peter Byrne and the late Dr. Grover Krantz.
The Hendersons' station wagon suffers heavy front-end damage including the eventual loss of the front bumper and driver-side headlamps, roof damage from Harry's head, the loss of the rear driver-side door and significant paint scraping down both sides after being run along the center divider on the freeway. Finally the wagon is stolen by Jacques. This is markedly similar, whether intentionally or unintentionally, to the damage inflicted upon Sergeant Murtaugh's station wagon in Lethal Weapon 2 (1989) - it suffers heavy front-end damage including the loss of front bumper and passenger-side headlamps, the rear driver-side door is knocked off, the roof is damaged (by flying toilet), both sides are scraped along a bridge railing, and the vehicle is finally stolen. The only difference is that the windshield is also shot out on Murtaugh's wagon.
Regarding the exit the Hendersons take from the freeway. This is the Lake City Way exit from the northbound express lanes of Interstate 5. The DOT highway crews changed the sign from "Lake City Way" to "Mt Rainier". If they simply continue on Lake City Way through Bothell, they will eventually hit Highway 2 which goes up Stevens Pass and into the Cascade Mountains. But they would still be a long way from Mt Rainier.
Richard Foley and Dana Middleton, the two news anchors listed in the credits, were real-life news anchors and talk-show co-hosts at Seattle's KOMO TV. Their brief appearance in the movie was from the set of their nightly local news magazine "Weeknight" which aired from 1983 to 1985, when it was replaced by the syndicated version of Jeopardy! (1984) when it moved from KIRO TV to KOMO TV. Another reporter is seen in the movie reporting from the actual newsroom of KOMO 4 News. Middleton and Foley also hosted "Northwest Afternoon," an afternoon daily talk show. Middleton left KOMO TV in 1993, and Foley followed suit in 1995.
The trivia items below may give away important plot points.
A sequel would have seen The Hendersons reunite with Harry. In some fans' opinions, the TV series based on the film could have been an alternate reality, exploring what would have happened if Harry had never gone back to his own family at the end of the film, deciding to stay with the Hendersons instead.