Jokes where you replace a word with something unrelated but similar sounding [duplicate]

So a friend of mine always works this type of joke into normal conversation and I always get a kick out of it.

Example:

Person 1: Why are you always hogging the TV remote?
Person 2: Because I am shellfish!

Obviously shellfish is not the correct word for that context, but it sounds similar enough that it works.

Basically what kind of joke is this called or what use of word replacement is that called?

P.S. Not required for a good answer, but if I wanted to respond to someone who has done this to me with the term "Grape job" what would be a good comeback/response?

I was thinking "well orange you nice", but feel like there is a more epic comeback that I just don't know of!

Solution 1:

This is a pun:

The use of a word in such a way as to suggest two or more meanings or different associations, or of two or more words of the same or nearly the same sound with different meanings, so as to produce a humorous effect; a play on words.

One could also call it a play on words:

a pun; a playful use of (esp. similar-sounding) words to convey a double meaning or produce a humorous effect.

(Both definitions from the OED.)