The Swiss have always been the guards of the pope. Swiss mercenaries have been bodyguards, ceremonial guards, and palace guards. Michelangelo actually designed the yellow and blue "costumes" for the Swiss guards or the guards of the Vatican. The Swiss guards (The ones at the Vatican) are the only Swiss guard left in Europe. The Papal Swiss guards are now at the Vatican but used to be in France.
The Swiss Guards also double as traffic cops for cars going into the Vatican, minus the court jester uniforms. Mommy is just outside St. Peter's Basilica with the Guard in the background.