Only two minutes long, but a lot of fun:
this webcast takes a look at "how idioms get their spellings (and meanings) reshaped into new variants, sometimes to the point of meriting dictionary inclusion" (in the words of interviewee Ben Zimmer, writing on
languagelog here). The pairs it examines include vocal cord/vocal chord, free rein/free reign, and shoe-in/shoo-in.
It involves cartoons (who are, apparently, ventriloquists).