They recently reran them in Nintendo Video; they originally came out in the week(s) leading up to the game's release.
On a related note, I would love if Nintendo actually made more Kid Icarus and Kirby: Right Back At' Cha cartoons for the 3DS. The Pokemon animated trailer would also be neat in 3D. Video services are doing more and more original material as bonuses to draw in people, so I don't see why Nintendo doesn't use Nintendo Video as a selling point of the 3DS with original content once a month.