“If he were reincarnated, what would he like to come back as?

Prince Philip's answer: "I would like to be reincarnated as a killer virus that would wipe out X% of the earth's population."”

When did he say this?

Yes! Phillip was a member of the Committee of 300.

https://www.womanandhome.com/life/news-entertainment/prince-philip-quotes-63435/

1. Commenting on the Duke of York's house in 1986: "It looks like a tart's bedroom"
2. Overheard at Bristol University's engineering facility: "It doesn't look like much work goes on at this University."
3. Approaching his 90th birthday, 2011: "Bits are beginning to drop off."
4. At a dinner party in 2004: "Bugger the table plan, give me my dinner!"
5. Shouted to the Queen from the deck of Britannia in Belize in 1994, who was chatting. "Yak, yak, yak; come on get a move on."
6. At the Scottish Women's Institute in 1961: "British women can't cook"
7. Talking to Tom Jones after his Royal Variety Performance in 1969, he asked 'What do you gargle with, pebbles?'. The day after, he added: "It's difficult to see how it's possible to become immensely valuable by singing what are the most hideous songs."
8. At Duke of Edinburgh Awards scheme in 2006. "Young people are the same as they always were. Just as ignorant."
9. On a visit to Canada in 1969: "I declare this thing open, whatever it is."
10. After being told that Madonna was singing the Die Another Day theme in 2002, the Duke of Edinburgh asked: "Are we going to need earplugs?"
11. At a project to protect turtle doves in Anguilla in 1965, he said: "Cats kill far more birds than men. Why don't you have a slogan: ‘Kill a cat and save a bird?'"
12. Talking about his equestrian-inclined daughter, Princess Anne: 'If it doesn't fart or eat hay, she isn't interested.'
13. When talking to designer Stephen Judge about goatee beard in 2009: "Well, you didn't design your beard too well, did you?"
14. When being questioned on when the Prince of Wales would succeed to the throne: "Are you asking me if the Queen is going to die?"
15. Addressing Elton John he said, 'Oh it's you that owns that ghastly car is it? We often see it when driving to Windsor Castle.' Later, at the Royal Variety Performance watching Elton perform in 2001, he said, "I wish he'd turn the microphone off."
16. About a Cambridge student who didn't recognize him: "Bloody silly fool!"
17. To a Scottish driving instructor, 1999: "How do you keep the natives off the booze long enough to pass the test?"

....it kind of does seem like the Queen will never die, doesn't it?

That sounded satanic

That sounded satanic