In Shakespeare's Richard III Glouchester says:
Now is the winter of our discontent
Made glorious summer by this sun of York;
Study.com refers to this line with particular emphasis on the word sun:
We can also ascertain from the first few lines that Richard is celebrating his family's victory. Richard's brother, Edward IV (they are the sons of the Duke of York, so in the second line 'son' is actually a pun for sun) has taken the English crown from Henry IV.
I understand that this can be referred to as a paronomasia--a synonym of pun, but I have a vague recollection that this is a specific kind of pun where a word is changed by a letter or two.