But Mr. Heathcliff forms a singular contrast to his abode and style of living. He is a dark-skinned gipsy in aspect, in dress and manners a gentleman: that is, as much a gentleman as many a country squire [...] (1.15)
Heathcliff's appearance reveals both his ambiguous racial background and his attempt to elevate himself socially. At this point in his life, he has transcended his background and gained control of both properties.
I was frightened, and Mrs. Earnshaw was ready to fling it out of doors: she did fly up, asking how he could fashion to bring that gipsy brat into the house, when they had their own bairns to feed and fend for? (4.46)
Mr. Earnshaw's addition to the family is unwelcome even by his wife, who may suspect more than we know. Is the child his? Has he been cheating on her off in Liverpool? Either way, she is no more welcoming of the child than are Catherine and Hindley. But because Mr. Earnshaw dies so early in the novel, we never get any sense of his motivation for bringing Heathcliff back to the Heights.
"Take my colt, Gipsy, then!" said young Earnshaw. "And I pray that he may break your neck: take him, and he damned, you beggarly interloper! and wheedle my father out of all he has: only afterwards show him what you are, imp of Satan." (5.65)
Even as a child, Hindley sees Heathcliff as a threat to his inheritance. But it is actually the way he treats Heathcliff that creates the orphan's drive to steal the inheritance. If Hindley had accepted him, things might have gone differently.
Ellen "Nelly" Dean
"We don't in general take to foreigners here, Mr. Lockwood, unless they take to us first." (6.7)
Isolated villagers like to remain just that. What's telling about this statement is that "foreigners" seem to be anyone not from Gimmerton. It's not like Frances or Heathcliff are from another country; these people just aren't too fond of difference.
"But who is this? Where did she pick up this companion? Oho! I declare he is that strange acquisition my late neighbour made, in his journey to Liverpool—a little Lascar, or an American or Spanish castaway." (6.40)
Heathcliff's foreign appearance is interpreted in many different ways. Like Nelly, Mr. Linton imagines a variety of exotic backgrounds for Heathcliff.
The cowardly children crept nearer also, Isabella lisping—"Frightful thing! Put him in the cellar, papa. He's exactly like the son of the fortune-teller that stole my tame pheasant. Isn't he, Edgar?" (6.36)
Isabella Linton associates Heathcliff's racial background with criminal types. Is this what later attracts her to him? Hmm…
Ellen "Nelly" Dean
"You're fit for a prince in disguise. Who knows but your father was Emperor of China, and your mother an Indian queen, each of them able to buy up, with one week's income, Wuthering Heights and Thrushcross Grange together? And you were kidnapped by wicked sailors and brought to England." (7.44)
With her love of stories, Nelly Dean inadvertently plants ideas in Heathcliff's head. Here are the seeds of his revenge against Hindley and Edgar.
Doubtless Catherine marked the difference between her friends, as one came in and the other went out. The contrast resembled what you see in exchanging a bleak, hilly, coal country for a beautiful fertile valley; and his voice and greeting were as opposite as his aspect. (8.53)
Edgar and Heathcliff present two opposing images, each of which appeals to a different part of Catherine. What's suggestive here is how closely the description of Edgar resembles the location of Thrushcross Grange.
It was a deep voice, and foreign in tone; yet there was something in the manner of pronouncing my name which made it sound familiar. (10.18)
Heathcliff has changed, but he retains his essential foreignness. Why he would have a foreign accent is anyone's guess. No matter what he does, Heathcliff is just plain different.
"Now continue the history of Mr. Heathcliff, from where you left off, to the present day. Did he finish his education on the Continent, and come back a gentleman? or did he get a sizar's place at college, or escape to America, and earn honours by drawing blood from his foster-country? or make a fortune more promptly on the English highways?" (10.8)
Foreign-looking by birth, Heathcliff's three-year absence compels speculation about travel to faraway travels. How did he get so much money? Where did he learn his sophisticated ways? All we know is that he has gone from being just plain Heathcliff to Mr. Heathcliff.