I was going to suggest "premalapropism" just 'cause its premeditated. It took a while to stop laughing.... I'm having a lamppost! Dang that is whey to phunny! Then I reconsidered and thought yeah weigh! Premalapropism was just perfect! Although I do love metaplasmus, it just doesn't completely describe the effect as intentional misuse persay more as to misspelling.