this is a reference to a segment on Downtown no Gaki no Tsukai ya Arahende (ダウンタウンのガキの使いやあらへんで!!) called "Yamasaki vs. Moriman", as seen here:
http://dynamite-shikoku.halfmoon.jp/459459/archives/2006/08/post_617.html
(ctrl+F for "ゴボウしばき合い対決")