Can You Use the Wii U GamePad on Original Wii? No - Proprietary 5GHz Link, Reverse Works

No. The Wii U GamePad uses a proprietary 5 GHz wireless link and hardware features (touchscreen, NFC, gyro, camera) that the original Wii cannot recognize or support.

Reverse Compatibility: You can use Wii Remotes, Nunchuks, Classic Controllers, and Balance Board on Wii U (for Wii mode and compatible Wii U games).