"Let the Wonk One In" is the fifthteenth episode of the second season (and sixty-seventh episode overall) of Randy Cunningham: 9th Grade Ninja and the third Halloween-themed episode of the show. It premiered on October 17, 2014.
The title is based off the 2004 Swedish vampire novel and the 2008 Swedish romantic horror film Let the Right One In.
The Forbidden Knowledge of the Shadow Warrior in the NinjaNomicon reappears, previously appearing in "Dawn of the Driscoll".
The part where Randy throws the NinjaNomicon and sucks the Halloweenja suit into it is reminiscent of the film Ghostbusters.
It's revealed in this episode that McFist is creeped out by retro Halloween music.
This is Rachel's second speaking appearance and first main appearance.
Rachel's line, "The power of cute compels you!" is a parody of the line "The power of Christ compels you!" from the 1973 horror film, The Exorcist, drawn from the Roman Catholic rite of exorcism of a demonic being.
The Halloweenja's magic circle is a reference to the Disney cartoon Gravity Falls.
In the background, a plastic figure snowman is wearing a hockey mask similar to that of Jason Voorhees from the Friday the 13th franchise.
