Here is the version I learned as a child in Takoma Park, Maryland (mid-1950's):

Ding,ding,ding,ding,ding
Here comes my wagon, my wagon
Hark! I hear my keeper calling me, me.
Ding,ding,ding,ding,ding
Here comes my wagon, my wagon
Take me back to the funny factory.
Like a little nut that falls
I'm a little cracked, that's all
Ding,ding,ding,ding,ding
Here comes my wagon, my kiddie car, my bus. Toot!Toot!