Other mistake: Season 1, episode 5 "iWanna Stay with Spencer": The "Fan of Hammers" has all the hammers pointed the same way. But when the hammer goes into the wall, it goes in backwards. It is also there through all the rest of the shows and even in season two, where in "iKiss" it has a black handle.
Other mistake: When Carly and Freddie are frantically trying to find a birthday present for Principal Franklin, they are talking in the kitchen and you can see a microwave above the sink. Carly then runs to the counter and grabs a microwave to give to him. Why would they have two?