Well, since somebody else posted a parody, I feel moved to share another.
My sister and I did this one a while back, one particularly silly evening,
so any blame is mine. This may work better for female dementians....

"Negligee"  (to "Yesterday")

Negligee,
I look stupid in this negligee
'Cause my butt sticks out this funny way --
Oh, why'd I buy this negligee?

Suddenly,
I am twice the girl I used to be;
Flab is hanging out all over me --
This negligee's a travesty.

Why it doesn't fit I don't know, I couldn't say;
I did something wrong when I bought this negligee.

Negligee,
I would like to take it back today,
But I threw the damn sales slip away --
I'll have to keep this negligee.
Hmm mm mm mm oo oo oooooo.