I'm sure that the song is played in E:

so the chords are E to A to B to E all the song repeated.

E chord:

E|--------|
B|--------|
G|--1-----|
D|--2-----|
A|--2-----|
E|--------|

A chord:

E|--------|
B|--2-----|
G|--2-----|
D|--2-----|
A|--------|
E|--------|

B chord:

E|--2-----|
B|--4-----|
G|--4-----|
D|--4-----|
A|--2-----|
E|--------|

to make it more interesting (chuck does so) play this at the beginning:

E|---------------------------------|
B|-----0-----0-----0---------------|
G|-----1-----1-----1---------------|
D|--2-----------2------------1--1--|
A|--------2------------2--4--------|
E|---------------------------------|

when the text comes in play this:
   
   E           A               B                    E
E|------------------------------------------------------------------|
B|-----0-----0-----2-----2-----4-----4-----4-----4-----0-----0------|
G|-----1-----1-----2-----2-----4-----4-----4-----4-----1-----1------|
D|--2-----------2-----------------4-----------4-----2---------------|
A|--------2-----------0-----2-----------2-----------------2---------|
E|------------------------------------------------------------------|
    When I was  a little biddy boy, my grandmother bought me a 
(make a little break to play the B part, Chuck does, too, because it's a 4/4 beat) cute little toy

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