One of my coworkers complained about someone who uses the word "aks" for ask.  This is among the common examples of phonetically switching sounds.  In linguistic phonetics, the natural morphing or switching of sounds is called metathesis.  An example is "Feb-you-wary" instead of February.

Some people pronounce the word "ask" as "aks".  This is "expecially" common in the black community.  Let's call it Ebonics.  Sure, I meant to say "especially".  I have read that "aks" is regarded as grammatically acceptable in speech; and unacceptable in spelling. I also read that "aks" is how the British and old Americans with British roots said it during the slave trading era.

Different people pronounce the heated sugar product as "carmel" or caramel.  Other Wiki examples include "calvary" instead of cavalry, "nucular" instead of nuclear, "purty" instead of pretty, etc.  It is amusing when a Texan complains about these metathetical utterances.  In Pasadena a street named Tatar is often pronounced "Tartar".   In Northern Houston the street Kuykendall is pronounced "Kirkendall".  In Texas many people pronounce pedernales and other words with an extra "R" such as "perdenales".   How should you pronounce Refugio?  This could lead us to other Texas examples, perhaps metathesis in Spanish  - or just going back to work.

http://metathesisinlanguage.osu.edu/resources/theoretical.cfm

http://en.wikipedia.org/wiki/Metathesis_(linguistics)

and expecially http://en.wikipedia.org/wiki/William_Archibald_Spooner if interested in Spoonerisms.