I've begun collecting words and phrases and even quite a few rhymes that may or may not match the music I'm having in my mind. Essentially it's just brainstorming at the moment. There are explicit expressions that I will NOT use. But I post them here anyway so you can see how I'm going about it. I intend to keep the song light on the one hand side and self-deprecating on the other - the idea is that Fanny was actually a very nice girl whereas "we" were horny little monsters.
Well, here is my "scrap book" for "Fanny" - uncensored:
what we'd think up she'd fulfill
she would rim, she would suck
she would be our devout three hole slut
contempt, scorn and derision, sneer, ridicule
behind her back but not to her face (tell it to..)
place, disgrace (bring disgrace on sb. / fall into disgrace)
she would tickle our pricks, she would tickle our pride
get our chubbies hard and teach us to ride
she'd teach us French, she'd teach us Greek
without having a single word to speak
fat farting Fanny -
the name we used to call her
the name we gave her
we poured scorn and derision on her gentle head
when we were feeling horny we gladly shared her bed
we'd run her down behind her back but smile to her face
we didn't really mind when she fell into disgrace
we tore her down, we used her up, we left her in the gutter
the shame I feel today makes my heart flutter (... makes my voice stutter ??)
she was so tender, was so kind, she was a bit like butter