My grandson's preschool teacher read them a Halloween book the other day which was an adaptation of the "There was an old woman who swallowed a fly." It was really cute, but I wish she'd taught it to them as a song, instead of just the book. Anyway, if I remember correctly it went,

There was an old woman who swallowed a bat
Why she did that, I don't know why,
Imagine that!

There was an old woman who swallowed an owl to catch the bat
Why she did that, I don't know why,
Imagine that!

There was an old woman who swallowed a cat to catch the owl to catch the bat
Why she did that, I don't know why,
Imagine that!

There was an old woman who swallowed a ghost to catch the cat to catch the owl to catch the bat
Why she did that, I don't know why,
Imagine that!

There was an old woman who swallowed a goblin to catch the ghost to catch the cat to catch the owl to catch the bat
Why she did that, I don't know why,
Imagine that!

I'll have to check on the ending as somehow you get to why she did it was to say, "Trick or Treat, Happy Halloween!"