In one of the final episodes of Drake & Josh (2004), a movie title listed on the reader board of the Premiere was "Now She's Carly." This was a reference to Miranda Cosgrove (Megan on Drake and Josh) moving on to play Carly on iCarly.
Sam's sound effect remote used on the show is the only one in existence. They have used the same remote since the pilot. Dan Schneider kept it in his home when it was not being used for filming to make sure the remote wasn't lost.
Freddie often speaks some of his lines in Spanish. Series creator Dan Schneider has often stated on his blog that the reason behind Freddie's random Spanish outbursts will be revealed in a future episode, but it never was. In the final episode, Freddie began to explain it but was interrupted.
Spencer's friend "Socko" has been mentioned numerous times throughout the shows run, and it became a gag in the writing room to mention Socko's friends and family members along with their professions. Socko makes Socks, his brother Tyler sells ties. Rob is a thief. Taylor is a tailor. Otto is a car salesman. Hattie is a hat maker, cousin Isaac is an optometrist, etc.
Most of the furniture in Carly's apartment was made by "Jellio," a company who makes furniture in the shape of cupcakes, ice cream, Rubiks Cubes and other random objects. To name a few, the hanging monkeys on the large window, the lamps, and the various colored gummy bear lamps were all designed for the show. Recently the Gummy Bear lamps have become available at the Jellio website.