Ed, Edd n Eddy 
  
Game Boy Advance 
  

Invincibility:


  At the Press Start screen, hold L + R and press Left, Left, Right, Down Down,
Up, Right.
Level Select:


  At the Press Start screen, hold L + R and press Left, Down, Down, Right, Right,
    Left, Down.
All Items:


  At the Press Start screen, hold L + R and press Left, Left, Down, Right, Right,
Up, Left.
   

Thanks to Revolution readers Maximillian, forces34 and Mark Henry!