The contribution presents three different issues that illustrate the various challenges that specialists on the Southern Dene languages face when dealing with contact scenarios. The three situations to be discussed involve: (1) shared idiosyncrasies in the phonologies of the source language and the target language leading to ambiguous outcomes (Spanish voiced fricatives before back vowels vs the dislike for labials in Dene), (2) regular external influence in the form of borrowings (Western Apache 〈Hṓ-sō〉 ‘bear’), and (3) borrowings that have been altered, almost beyond recognition, under the action and effect of internal mechanisms (Diné bizaad gohwééh ~ ’ahwééh ‘coffee’).