Given that Charlie (like Parson) understands leetspeak, as well as the Stupidworld references inherent in Erfworld names, it is likely he is familiar with Parson's World. Further evidence for this supposition comes in the fact that Erfworlders are conscious of Charlie's "otherness," much as they are conscious of Parson's "otherness." Like Parson, Charlie seems to have some capacity bend, or work around the rules of Erfworld. Moreover, he appears to feel some degree of kinship with Parson. Finally, Judy's account of the history of Efbaum implies that Charlie held a role analagous to the Wizard of Oz. Just as the Wizard was a man from "a" stupidworld, who found himself transported to the fantastical land of Oz; so also Charlie may be a man from "the" Stupidworld, who found himself transported to the fantastical land of Erfworld.
Given that Parson comes from Ohio and Judy comes from Kansas, it is likely that their home planets are one and the same. However, Judy is unusually short for a Stupidworlder and her name is the sort of reference Parson would be capable of recognizing as one of Erfworld's jokes, possibly implying an alternate version of Stupidworld. On the other hand, Parson also has a reference for a name, with "Parson Gotti" being an anagram of "protagonist".
Given that Judy wears an old fashioned dress, is surrounded by Wizard of Oz references, and her description of Kansas as "flat, windy, pig-boop smellin’ rural Kansas", it is also possible that Judy is from early 20th century Stupidworld, as opposed to Parson who is clearly from the early 21st century.
The evidence we have for Stupidworld resembling the Real World is:
- Since Parson is surprised by things popping into existence, we can assume it is a continuous world rather than a discrete world like Erfworld.
- Parson needs to learn the rules of magic. This implies that the various forms of magic in Erfworld do not exist in Parson's World, or if magic exists, that it is significantly different from what he is familiar with.
- Parson had pizza stains on his T-shirt, implying the existence of fast food and free enterprise (also supported by his statement refering to his employment at Kinko's).
- More importantly, this implies that people and things are not cleaned at the start of each day, as they are in Erfworld.
- Parson was a Game Master of a Role Playing Game, and has shown experience with gaming with miniatures. This implies gaming as a leisure time activity. The existence of leisure time implies an automated society, or at least one that has gone through an industrial revolution,
- Speculation of automated society is supported by the fact that Parson is seen driving a car, which have to be mass-produced in order for Parson to afford a one.
- The Internet exists with many noticeable similarities to the real world - Parson writes a webcomic, and mentions Youtube in LIAB 45.
- Parson is from Columbus, Ohio, and Judy from Kansas, which likely indicates that the United States (or some equivelent thereof) exists in Stupidworld.
- Judy uses the word "kill" and "year", terms unknown to the inhabitants of Erfworld.
On the other hand, there appear to be at least minor differences:
- Easter marshmallow Peeps do not become solidly crunchy by July in the Real World.
- ...or at least, not the same year. Even a single complete year-plus (to July) of climate controlled counter-top storage is insufficient to render Real World Peeps crunchy to more than the outer eighth inch. Circa the one-and-a-half to one-and-three-quarters year mark, Real World peeps will be crunchy throughout; thus, crunchy Easter chick Peeps in July implies a minimum age of over two years. This discrepancy may not mark a difference per se, but might instead indicate that the lead times and single-minded focus Parson commits to his planning are more obsessive than even those around him realize.
From this preponderance of evidence, it is best to assume that Stupidworld is Earth in every respect unless stated otherwise.