Or does it happen always - when a Muggle finds out something - poof! - memory erased?
Are there any circumstances when a Muggle doesn't have to be Obliviated after they find out about the existence of magic?
81When those muggles are MiB agents, it is the wizards who lose the memories.– Satellite of SinMar 24, 2017 at 7:26
47@I Love You: I can just imagine Arthur Weasley lovingly admiring the ingenuity of a muggle-crafted obliviator, right before he gets neuralyzed with it.– delinearMar 24, 2017 at 8:19
10@ILoveYou Welp, that's a crossover I didn't know I needed in my life.– DeliothMar 24, 2017 at 18:57
4Hermione's parents aren't obliviated. I don't even see the problem with muggles knowing about magic. Lot of fanfics out there about muggles finding wizardry gear and causing havoc. Even they don't get obliviated. You should check some out.– NickMar 26, 2017 at 4:29
5@Nick - fanfics aren't canon...– MithicalMar 26, 2017 at 6:37
Parents of Muggle-borns are allowed to retain their memories, and we see Hermione's parents in Diagon Alley.
"So you don't think I'm a match for Lucius Malfoy?" said Mr. Weasley indignantly, but he was distracted almost at once by sight of Hermione's parents, who were standing nervously by the counter that ran along the great marble Hall, waiting for Hermione to introduce them.
Harry Potter and the Chamber of Secrets, chapter 4
And we know that the Dursleys also have memories of the Wizarding world, and Petunia knew all about magic when Lily was in school:
"...I'm sorry, Tuney, I'm sorry! Listen -" She caught her sister's hand and held tight to it, even though Petunia tried to pull away. "Maybe once I'm there - no, listen, Tuney! Maybe once I'm there, I'll be able to go to Professor Dumbledore and persuade him to change his mind!"
Harry Potter and the Deathly Hallows, chapter 33
"Knew?" shrieked Aunt Petunia suddenly. "Knew! Of course we knew! How could you not be, my dratted sister being what she was? Oh, she got a letter just like that and disappeared off to that - that school - and came home every vacation with her pockets full of frog spawn, turning teacups into rats. I was the only one who saw her for what she was - a freak! But for my mother and father, oh no, it was Lily this and Lily that, they were proud of having a witch in the family!"
Harry Potter and the Sorcerer's Stone, chapter 4
See also @Colin__s's answer, which has another excellent example.
19grumble grumble Sorceror/Philosopher grumble Mar 25, 2017 at 15:49
4@ArtOfCode - I actually wish that they hadn't switched it for the American version. Mar 25, 2017 at 17:16
4Well, it's in your power to change the name in your answer :) Mar 25, 2017 at 18:08
3@Gallifreyan - nah, can't do that. It wouldn't be accurate, because I'm quoting from SS, not PS (unfortunately). Mar 25, 2017 at 18:10
3They won't know that. Also, it's fairly easy to use a certain search engine with certain search terms to verify the accuracy of your quote. Mar 25, 2017 at 18:18
As we learn from Chapter 1. The Other Minister in the Half Blood Prince, the muggle prime minister of the day is told of the ministry, and magic, with nothing to suggest they're oblivated when they leave office.
In the sixth book they prove, that he was NOT obliviated:
It was precisely this sort of behavior that made him dislike Fudge's visits so much. He was, after all, the Prime Minister and did not appreciate being made to feel like an ignorant schoolboy. But of course, it had been like this from his very first meeting with Fudge on his very first evening as Prime Minister. He remembered it as though it were yesterday and knew it would haunt him until his dying day.
Harry Potter and the Half-Blood Prince,chapter 1
4In the sixth book they even tell, that the muggle minister is NOT obliviated by showing him remembering all the visits of the "other" minister, as he calls him....– TodeMar 24, 2017 at 7:36
Good one, I forgot this! +1 Mar 24, 2017 at 7:38
7Is this quote from the POV of a current or former PM? If current, it is not evidence that obliviation won't come at the end of their time in office, just that it has not happened yet (and doesn't know it will come). Another question specifically states a former PM was not obliviated at the end of their term, but it would be good to see a quote that specifically supports that. Mar 24, 2017 at 13:54
5I don't have the quote now, @Mr.Mindor, but it's implied. IIRC Fudge suggests that he wouldn't say anything because of how ridiculous it would sound, as such there is no reason to do anything.– ColinMar 24, 2017 at 14:19
10@Colin__s, the quote goes, "But then," bleated the Prime Minister, "why hasn't a former Prime Minister warned me –?" At this, Fudge had actually laughed. "My dear Prime Minister, are you ever going to tell anybody?" (Rowling, p. 12, Harry Potter and the Half-Blood Prince).– user72928Mar 24, 2017 at 17:32
Apparently, marriage is a circumstance. As Seamus Finnigan points out in the first movie, it was a "bit of a nasty shock" for his Muggle father when he found out his wife was a witch.
An obvious exception are the families of Muggle born Witches and Wizards. Lots of Muggle borns are mentioned in the books such as Hermione, Dean, Ted Tonks etc. We see that Hermione's parents were exposed to the Wizarding Community, visited Diagon Alley and even met the Weasleys.
Another instance we see is that of the Dursleys. We don't know how informed Vernon was about Magic before Harry ended up at their doorstep but he knew enough to refer to the Potters as "their lot".
Comment: Are those the only exceptions? Could a Muggle do something important that they'd be seen as worthy of keeping their memories? – Elisa Elisija
Reply: Yes. The only instance I can think of is... Becoming the Prime Minister. From the interaction observed between Cornelius Fudge and the British Prime Minister we see that though former PM knew about the Wizarding Community, he was not obliviated when his term ended in the office. The assumption that no one would believe a word about magic is considered a sufficient safeguard for this
Also squibs (wizard drop outs), people who couple with other races (giant/human couples), people working in the wizarding world who aren't wizards (the hippogryph executioner comes to mind).
5Pretty sure the Hippogriff executioner (Macnair) is a wizard.– Rand al'Thor ♦Mar 26, 2017 at 21:49
5Squibs aren't 'dropouts', they're people born into wizarding families with no magical ability. Can't drop out if you never qualify to attend...– RobotnikMar 27, 2017 at 3:07
2Are any of these Muggles?– ibidMar 27, 2017 at 4:27
4Sqibs aren't Muggles - they're Sqibs. Half-breeds aren't Muggles - they're simply only half human. Muggles don't work in the Wizarding world. The example you mentioned, Macnair, is not only a wizard, he's a Death Eater. Sooo.... Mar 27, 2017 at 7:08