Shows Dan has worked on have a history of spinoffing popular, young characters from previous shows.
Amanda Bynes from All-That went to star in The Amanda Show.
Drake and Josh from The Amanda Show went to star in Drake And Josh.
Miranda, Jimmy, and Nathan who all appeared in Drake And Josh went onto star in iCarly.
Jamie was on All-That and later appeared on Zoey 101.
Kenan and Kel from All-That went to star in Kenan And Kel.
Lil' JJ, who appeared late on All-That, went to star in Just Jordan.
Kablam! spinoff from All-That.
Victoria went from Shelby, on iCarly, to Tori on Victorious.
Jeremy went from a few characters on 'Amanda Show to Lewbert on iCarly.
It's always the younger stars that become the staring characters. The only two people I can think that fit that are Noah ("Gibby") and Reed ("Nevel"). Noah seems like the best choice (being so popular and all), and he's only around fourteen making him the youngest main character.