People with the Boston accent do that. If a word ends with a vowel sound, and the next word begins with a vowel, they'll add in an R at the end of the word. And likewise, they only pronounce Rs if the next letter is a vowel, and otherwise the R is silent (resulting in "hard" and "park" sounding like "hahd" and "pahk" for instance). The latter is the defining characteristic of all non-rhotic accents, but adding in the r if the next word begins in a vowel is specific to the Boston accent.