Berserk Button: One particularly hilarious example in the movie; when Fred is told his "girlfriend" has moved, he goes on a rampage and destroys his living room. Because of his sunny disposition, he cleans up afterward.
With iCarly in Fred on iCarly and the iCarly episode iMeet Fred—Fred is fictional in the iCarly universe, but iMeet Fred features two exclusive Fred videos, both featuring iCarly characters (the second of these videos can be seen here).
DVD Commentary: The first movie has one by director Clay Weiner, writer David Goodman, and actor Lucas Cruikshank.
Depending on the Writer: On just how dark it gets. The original youtube videos depend on a lot of dark humour, the animated series is dark as well, and manages to be even crueller to the characters then the videos. The movies are pretty clean, with some things from the original hinted at and some dark comedy by Nickelodeon standards. The TV show is squeaky clean, with maybe a couple adult-ish jokes scattered throughout.
Even Evil Has Standards: Kevin one time pretended to be Judy, saying that he and Judy had broken up, and wanted to date Fred. When Judy found out she stated that was too far, though Fred thought Judy was only acting.
The web videos count too, even though they were on youtube, the darker jokes are slipped in subtly due to Fred's limited knowledge of the world combined with the fast pace of the videos most people don't catch on as to what Fred is actually talking about.
Overly-Long Gag: In the first movie, when Fred's faced with a car repairman who doesn't speak English, he thinks he is being messed with and proceeds to run away screaming, while we are shown brief shots of different areas (like near a fence, on a railroad track and even on a rollercoaster track). This continues until he runs into a live dam.
Parental Abandonment: His mom loves bars and staying out late and is almost never there, and his "rock star" dad is on Death Row. The first movie implies that Fred's dad actually lived nearby (until the movie's events actually occur), and was never in jail (or a rock star), but FRED makes a Diorama has Fred's dad appear in jail.