My first browser extension, live at the Google Chrome Web Store!
It's Simple™ enough - text nodes are selected from the DOM, and every word is translated independently. Each word in each node is translated into its International Phonetic Alphabet (IPA) spelling, and each IPA character within the word is replaced with its "dranzleyduhd" version.
Also, after a page is translated, text added after the initial translation (article pop-ups in Wikipedia, emails after opening from the Gmail inbox, etc.) is handled by translating individual text nodes added to the DOM using a simple listener.