A mondegreen is the mishearing or misinterpretation of a phrase as a result of near-homophony, in a way that gives it a new meaning. (eg. “pre-Madonna” instead of “prima donna”)
The unintentionally incorrect use of similar-sounding words or phrases in speaking is a malapropism. (eg. “intensive purposes” instead of “intents and purposes”)
If there is a connection in meaning, it can be called an eggcorn. (eg. “old timers” instead of “Alzheimers”)
If a person stubbornly sticks to a mispronunciation after being corrected, that can be described as mumpsimus.
Just for the sport of it, how about “reverse Mondegreens”:
Some nonsensical lyrics can be interpreted homophonically as rational text. A prominent example is Mairzy Doats, a 1943 novelty song by Milton Drake, Al Hoffman, and Jerry Livingston. The lyrics are a mondegreen and it is up to the listener to figure out what they mean.
The refrain of the song repeats nonsensical sounding lines:
Mairzy doats and dozy doats and liddle lamzy divey
A kiddley divey too, wooden shoe
The clue to the meaning is contained in the bridge:
If the words sound queer and funny to your ear, a little bit jumbled and jivey,
Sing “Mares eat oats and does eat oats and little lambs eat ivy.”
The listener can figure out that the last line of the refrain is “A kid’ll eat ivy, too; wouldn’t you?”, but this line is sung only as a mondegreen.