Acting for Two: Alton often plays two different characters in the same scene (generally one of them as himself), sometimes doing a cut between himself and the alter-ego, and sometimes using camera trickery to put him and the alter-ego in the same shot.
In Season 7 episode "The Cookie Clause", Alton Brown mentions using cocoa powder to hide mistakes with coloring frosting. Santa turns to the camera, stroking his chin and murmuring "cocoa powder". The same actor who played Santa also plays Cocoa Carl, one of Alton's Sitcom Arch Nemeses.
The same actor also showed up as an appliance salesman in the souffle episode, leading to a You Look Familiar moment at the end of the scene.
Doing It for the Art: Alton never made any money off of Good Eats itself, instead pouring what would have been his salary back into the show's budget. He makes all his money off of merchandise, writing, and advertising (like the series of ads for Welch's grape juice).
One of the producers even agreed to construct a new home around a kitchen specifically designed to allow for production of the show within said home/kitchen (this would be the "set" used for Seasons 5-8). Complaints from neighbors eventually forced the show into a lookalike studio set for the remainder of the production run.
And while we're at it, it might be no coincidence that Alton voiced himself in a Good Eats/Archer crossover (yes, this happened, as a DVD bonus). Alton beat the piss out of Sterling.
Real-Life Relative: Alton's mother appears in "Romancing The Bird"; his (now deceased) grandmother was in two episodes (fruitcake and biscuits); his daughter appears in several episodes; however, his wife (who is also a producer) did not appear outside of the curtain call on the 10th Anniversary special.
Science Marches On / Tech Marches On: Often, Alton's explanations and guidelines on whether to do (or not do) and use (or not use) a certain thing change with the seasons due to new studies, new technology, or changes in commercial foods. Sometimes, he will address his previous guidelines and explain how things have changed—but this doesn't stop Negative Nellies from pouncing on what they think are examples of Alton not doing his homework.
Of particular note, Alton's stance on frying machines.Explanation In early episodes, Alton eschewed the use of them in favor of a dutch oven or pot with a fry thermometer. By the first "Man Food Show" episode he worked with a electric fryer, explaining that modern models work better and are safer to use (and was a better approach for the corndogs he was making as it allowed the food to stay in the fat while the sticks stay out)... but he went right back to using the dutch oven and thermometer in the next season. Eventually, in the Season 10 episode "Tortillas Again", he explained why he went back to dutch ovens, saying that despite all the improvements, electric fryers still don't manage heat very well in terms of maintaining temperature between each batch, which leads to greasy food. He's also said that a heavy pot or dutch oven is better because it allows the cooking food more freedom to move around and thus cook more evenly.
Then there's Alton's use of shortening.Explanation In early episodes, Alton used vegetable shortening in quite a few episodes—for example, when making biscuits. In the Season 3 episode "The Case for Butter", Alton showcases the then-recent studies that revealed that the trans fats used in shortening are actually less healthy than the fats in butter. Since then, several vegetable shortening manufacturers have introduced "low" or "zero" trans fat versions of their products, but as Alton notes in the Season 9 episode "The Waffle Truth", companies can claim their products are fat free if the serving they recommend has less than half a gram of fat.
Curiously enough, some of these changes appear due to Brown's and Food Network's influence. Items like Microplane graters and chimney starters were relatively hard to find back in 1999, but today are available at any store with a cooking section or barbecue display.
What Could Have Been: On an episode of the Nerdist AB mentioned that he was able to figure out a way to effectively cook a whole pig with just 75 dollars worth of gear from the hardware store. Unfortunately, the executives at Food Network vetoed it because they said no one would actually try it.
Every time Alton says "but that's another show"...and we never got that episode.
W, aka Vicki Wong, is played by Alton's chiropractor, Vickie Eng.
In the book Good Eats: The Early Years, Alton says that everyone who works on the show does so with the understanding that, one day, they'll be appearing on-camera in some capacity. Thus many characters in the series are members of the staff (exceptions are actual food experts such as Deb Duchon the nutritional anthropologist, Shirley Corriher, and a few recurring characters that are hired actors such as Marsha, Elton, Cocoa Carl, Chuck, etc).