New Scientist :
Eggcorns - derived from a misspelling of "acorn" - are a particular type of language error. Though incorrect, eggcorns are often more satisfying or poetic than the correct word or expression. If you didn't know how to spell the word "acorn", then "eggcorn" is a logical and satisfying alternative.
There's even a site devoted to eggcorns, the Eggcorn Database. As most of the eggcorns I've personally overheard (or, ahem, inadvertently come up with myself) are oral rather than written, I don't think I can contribute them to the database.
But I'll share some with you anyway... (maybe more of a mixed metaphor?):
- Banging her own trumpet (guess what that's a cross between!).
- As the flies go (for "as the crow flies...").
- On the horns of a quandary.
- Up a gumtree without a paddle.
"She's always rubbing herself up against a brick wall".