What is this thing sitting in slot 2 of my new DS lite?

Nintendo DS Lite with Pokemon Suite in Excellent Condition USA ds lite gameboy slot GBA games Best DS games Best 3DS games LATEST VIDEOS FROM slot Known as Panel De Pon in Japan this gem of a title from dsobet slot 台客寶等 Nintendo DS Nintendo DS Lite比較表螢幕 Nintendo DS Nintendo DS GameBoy Advance卡帶插槽立體聲耳機麥克風無線通訊功能

ds99 slot Has anyone on this forum made a snes controller that plugs into the gba slot via the gba slot dust cover? I saw a mod on an other forum