There were a couple of things in this episode that showed Malcolm acting like a genius at the age of four, such as playing with a chemistry set. However, until the pilot episode (which was when he was 11/12), no one had any idea and it was presumed that he acted like the other kids, not playing with science equipment.
During the cold open, just after the ball is thrown into the sewer, a lighting rig can be viewed quite clearly to the left of the screen.
Goof: In the flashback prior to Malcolm's birth, toddler Reese is 2 years old and has blue eyes. But Reese is supposed to be a little more than 1 year old than Malcolm and has brown eyes.
When Lois goes into labor with Malcolm, she runs outside taking Francis and Reese with her. When Francis says "You're a liar, you're a liar!" watch the back window of the car and you will see the camera and camera operator reflection in the window.
While Francis is in the diner, you can see Dewey in the background on the television screen (upper left of the screen) on what appears to be a news broadcast that says Toxic Orphan.
In a flashback scene, Francis says "Now we know, pigs can swim, cows can't". Cows can, in fact, swim.
Several of the fair folk are actual Guinness Book of World Record holders who also perform around the country.
When Stevie and the boys are coming up with a plan to go to the fair, they decide to each say they are staying at the other's house and go to the fair. Malcolm calls it a double alibi. It is popularly referred to by junior high and high school kids as a Round Robin.
The large knot on Reese's leg is called a fracture blister. Sometimes when a leg breaks, swelling in the bone (called compartment syndrome) causes a large knot to form. The longer it goes untreated the darker and larger it gets, as Reese mentioned was happening.
This is the first time that one of the family members inadvertently injures Craig or his property and he moves in with them. This becomes a recurring theme throughout the series.
If you look closely in the scene where Malcolm breaks his microscope and Reese beats himself up, you can see a large Charmander plushie in the room.
Craig's apartment number is 2816 1/2.
Craig's cat is called Jellybean.
The address number for their house is 12345.
When Francis gets pulled over, his window is open and closed between shots.
In the second last frame that Hal bowls, he takes a drink, walks up the to lane, unzips his pants and says "Gesundheit" and bowls a strike, when he turns around he sees a guy leaving to go to the bathroom and starts pleading with him that everything has to be in the same place and finally the guy says he'll stay. Hal then turns around to repeat the steps he's taken, including unzipping his pants; however, he never zipped them back up because he was too busy pleading with the guy.
Goof: Malcolm said that black Thursday was one of the causes of the Great Depression. The stock market crash was on a Tuesday, not a Thursday.
This episode begins Reese's love affair for cooking, which persists throughout the series.
Shortly before the teacher announces the cooking competition, Reese takes either chicken or turkey, garnished with watercress, out of the oven; however, the heat of the oven would have wilted the watercress. Garnishes are added just before a dish is served -- they're never placed on food while it's in the oven.
If you listen very closely while the music is playing, you can hear a heartbeat monitor beeping and then go in the continuous beat which means cardiac arrest. It then switched to Helmut dragging what appears to be a body down the hall.