The Secret Service codename for Vice-President Joe Biden is "Celtic", but the Gaelic links to Australian rules football must have puzzled the small troop of burly blokes with earpieces hovering at the MCG boundary line as their charge strode onto the green.

Only a few minutes earlier a man dressed head to toe in a navy blue onesie had perched on top of a hovercraft, spinning donuts wildly across the ground to entertain the crowd.

US Vice-President Joe Biden attends an AFL match between West Coast and Carlton at the MCG. With him were Maxson Cox and Foreign Minister Julie Bishop.

It's an oval shaped ball, and you kick it, AFL chief Gil McLachlan appeared to instruct his slightly bemused-looking US visitor before Carlton took on West Coast on Sunday.

But the MCG has long been familiar with Americans, well before the arrival of US recruit Mason Cox, the Collingwood ruck man from Texas, who later sat beside Biden in the stands.