So Long, and Thanks for All the Fish is the title of a book written by Douglas Adams. It’s part of the Hitchhiker’s Guide to the Galaxy cycle.
In the book, the dolphins leave this message to mankind before leaving Planet Earth, just before it is destroyed.
Fans of this book (including me) often use this phrase humorously to say goodbye in informal situations.
However, if you are not a fan, you can still use So long when saying goodbye to someone:
- So long, Chris. See you tomorrow!
- Take care.
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