When Suzie goes looking for Scott she passes some sort of odd mask-like decoration that seems to have green eyes. The eye color is similar to the eyes of Mona Wilder (the green-eyed woman who freed Dirk) and the mask resembles the one the forest witch wears.
The paintings in the "house within a house" that Dirk passes, in order, are: a boy wearing a cowboy hat and raising his arms, a boy in a cowboy hat holding the magical "air gun", the Cardenas Family Motor Lodge as it might have appeared several decades ago (the billboard sign in that painting is the same one as seen in the present time), an unidentifiable figure by a tall tree, and a small white boat (it is in shadows and hard to see clearly if it is in a field or a body of water).
The monster's song is "The Purple People Eater" by Sheb Wooley. Contrary to popular belief, the song describes a "one-eyed, one-horned" monster that eats purple people (as the main lyrics make clear) and itself is not necessarily purple.
Bart calls the enchanted land "Wendigo" instead of "Wendimoor" by mistake. A Wendigo is actually a mythical beast from Algonquian legends.
Todd wakes up to Sherlock's cat, Mustard, meowing. Although the cat is not seen, Sherlock mentioned it in Space Rabbit (2017) when he gave Todd his cat's pills to help with Todd's Pararibulitis.