The Wii Classic Controller was initially intended as an accessory to provide a comfortable way of playing Virtual Console games on Wii as well as facilitate traditional control options to certain games suitable to that playstyle.
The button layout and general shape of the controller is based on that of the SNES controller with an additional pair of analog sticks placed similar to how they appear on a PlayStation controller. Additionally, a small second set of shoulder buttons, named ZL and ZR are accessible between the main L and R shoulder buttons. This is the first time a Nintendo controller had both two full analog sticks and two additional shoulder buttons. The ZL and ZR buttons are an amalgamation of the Z-trigger on the N64 and the singular Z-button placed above the R-shoulder button of the GameCube controller. Notably, the L and R shoulder buttons are analog buttons but they are never utilized as such in any software since the system's main controllers (the Wii Remote and Nunchuk) would not support that feature. Additionally, the controller features a strange clip mechanism (which was never used for anything) that would likely have let players attach the controller onto another device and release it again by pushing down the little latch button in the center between the ZL and ZR buttons. Rumble is not supported in this controller but the attached Wii Remote would still produce the rumble feedback while the Classic Controller was being used.
The controller was only available in the basic white Wii color until the release of Monster Hunter G in Japan, which bundled in a special edition with a unique Monster Hunter-inspired design on a blue shell with coal-colored sticks and buttons. This would mark the start of Capcom's collaboration with Nintendo on special controllers specifically tied to the Monster Hunter-series as they would eventually go on to work closely with Nintendo's hardware team during the development of the Wii Classic Controller Pro which would replace this basic model in 2009 alongside the launch of the first original Monster Hunter game on a Nintendo system with Monster Hunter Tri.
The Wii Classic Controller is compatible with the NES Classic and the SNES Classic mini consoles since their controllers use the same accessory port as the Wii Remote, which also makes their NES and SNES controllers compatible with Wii Remotes, conversely.
A dedicated version of the Classic Controller that is modeled to be a replica of the Super Famicom/PAL SNES Controller was eventually released in Japan (in April 2008) and PAL regions via Club Nintendo as an exclusive reward item (2010 in Europe for 7000 Stars, 2011 in Australia for 3000 Stars). It looks exactly like a SNES controller except its cable has a Wii Remote accessory connector at the end and plugs into Wii Remotes (and could also be uses on the aforementioned NES Classic and SNES Classic mini consoles and is interchangeable with their controllers).