When Carly, Sam and Freddie try to pull Spencer out of the air duct by his ankles, they accidentally pull his pants off (by the ankles). Immediately in the next shot, literally from one frame to the next in the same scene, Freddie is holding them by the waist as he jumps backward until Spencer asks presumptuously, "Did my pants come off?".
When Duke lifts the refrigerator there is a disconnected cord on the ground plugged into the wall. When Freddy approaches the wall, there is nothing plugged into the wall.
When Spencer crawls into the heating duct and gets stuck, there is a vent screen beside his left shoulder that lets light in that shines on the opposite wall of the duct; this vent would be located under the stairs - but in shots showing the stairs there is clearly no vent.
In the iCarly studio, after the gang discovers the chicks have hatched they go online to find out how long they have to find them - Freddie says 56 minutes - then Sam asks if they can have lunch first and is told "No", then they run downstairs - once downstairs both Sam and Carly have magically changed clothes.
Spencer turned the heat up to 90 degrees. The iCarly trio should have gotten all sweaty, especially since they were in long sleeves; however, they showed no reaction to the temperature at all.
The chicks used in this episode would be, naturally, two weeks old. They are meant to be newborn.
All six chicks hatched in the same day. This is extremely rare, and even impossible, as usually only three would hatch with large amounts of time between the hatchings.
The chicks escaped from the incubator. This would also be near impossible, as incubators are designed to contain chicks/ducklings. If they did escape, the top of the incubator should have been evidently loose.
Carly decides to stop the search for the final chick as time has run out. However, a chick's death would not have been timed upon their escape like the trio made out.
It would be impossible for a chick to get inside the wall unless there was a hole somewhere, which is unlikely.