A pretty funny song by the comedy acappella group Da Vinci's Notebook.

E (022100@1)          AbWhenever (xx1114@1)life gets you down
             A (x02220@1)     AmKeeps (x02210@1)you wearing a frown
          B (x2444x@1)   Bb (x1333x@1)     A (x02220@1)     Ab (xx1114@1)EAnd (022100@1)the gravy train has left you behind
               E (022100@1)        AbAnd (xx1114@1)when your all out of hope
             A (x02220@1)         AmDown (x02210@1)at the end of your rope
       F# (244322@1)                        BAnd (x2444x@1)nobody's there to throw you a line

AIf (x02220@1)you ever get so low
                AmThat (x02210@1)you don't know which way to go
     E (022100@1)                       E7Come (020130@1)on and take a walk in my shoes
       F#Never (244322@1)worry 'bout a thing
 F# (244322@1)Ab (xx1114@1) AGot (x02220@1)the world on a string
            B (x2444x@1)                        
Cause I've got the cure for all of my blues (all of his blues)

E (022100@1)        Ab (xx1114@1)C#mI (x13321@4)take a look at my enormous penis
          A (x02220@1)             B (x2444x@1)     E (022100@1) E (022100@1) Eb (x43121@3) EAnd (022100@1)my troubles start a-meltin' away (ba-doom bop)
                 E (022100@1)        Ab (xx1114@1)C#mI (x13321@4)take a look at my enormous penis
          F# (244322@1)                     BAnd (x2444x@1)the happy times are comin' to stay (be-doo)

AI (x02220@1)got a sing and I dance
         AmWhen (x02210@1)I glance in my pants
        E (022100@1)                      Eb (x43121@3)C#mAnd (x13321@4)a-feelin's like a sun shiny daaaaay
                 A (x02220@1)        B (x2444x@1)E (022100@1) Eb (x43121@3)name="chord_xx0232@1">D  C#mI (x13321@4)take a look at my enormous  Pee--e--e--nis
          A (x02220@1)        B (x2444x@1)      E (022100@1) E (022100@1) Eb (x43121@3) EAnd (022100@1)a-everything is goin' my way (ba-doom bop)

And that's basically it. The rest of the song uses 
the same chords. Just listen to it and you should 
figure out the structure.