This is the first and only time Ms. Frizzle is shown to be on cafeteria duty besides solely being a teacher and bus driver. It is likely she may be substituting for one of the cafeteria staff.
The cafeteria scenes in the beginning and end of this episode show the outside of Walkerville Elementary School and its surroundings being set in the late autumn, presumably in November.
When the class goes on a field trip, the screen transitions rather than show the Bus transforming when compared to other episodes. The only time the Bus is shown transforming is near the end when they escape from the Arctic after re-heating the Bus, and transitioning back to school, presumably on the next day. This is one of the few episodes where the Bus is only seen when on field trips.
When Ms. Frizzle gets distracted looking at the control panel while driving the Bus until she ends up driving through the cold water, it's a premonition that predicted the dangers of texting while driving when cell phones with the text-messaging feature would become commonplace in the next decade later and other means of distracted driving leading to accidents.