A quick shot of a New Super Mario Bros. title on the Wii U GamePad gives away the unannounced feature.
The Wii U appears to have some kind of built-in achievement system as part of the Miiverse.
A video shown during the pre-E3 Nintendo Direct conference was designed to show off how the Miiverse social networking features could be integrated into in-game content. The example video, from a New Super Mario Bros. game, included a gold bar with the text that read "Cleared in under 100 seconds."
Included with the "achievement" was a celebratory message from the player who earned it. Seeing as the Miiverse is system-level functionality, it is safe to assume that these achievements are also included at system level.