The simplest toy is a grandparent

If you give a tin cop a motorcycle,
don't be too surprised
if he starts behaving strangely
once he knows he's motorized.

When he straps a helmet on his head
and winds up the friction wheels below his feet,
you'll see him pop a wheelie
and go racing down the street.

Pretty soon he'll find he's fond 
of doing motorcycle tricks.
He'll be jumping over toy cars and trucks
and buses just for kicks.

So remember this advice:
Tin cops in a police car drive like a grown-up
But if you put them on a motorcycle
they won't slow down - even  for a donut.