When I read Hitchhiker's Guide, I pronounced it b'tell-jew-EEss

There's a thought that:

Never make fun of people for mispronouncing a word. It means they learned it by reading

Best I understand, this is a quote without a known attribution

My dad was an astronomer, and as a toddler I thought it was the funniest name for a star. Then the movie came out and I was bugged that they misspelled the name for the promotional posters (but not in the movie itself).

colloquially it might be beetlejuice, but traditionally it's more like betelgyse or betelgoosa

But only in English. In German though... it's very strangely pronounced. Beite-zeus (but the z is soft)