Here is a line from a student's assignment: 'By the way, there was an interesting case at the party. You probably didn't hear about it.'
I feel something is wrong with 'an intersting case'.
Is it possible to say:'By the way, an interesting thing happened at the party.'
Thank you in advance.
Depending on the context, it sounds strange. I could find contexts to suit the line, though.
However, assuming a "normal" context which would include a party, your option sounds better. Also, of course "something interesting", among other options.
Please be aware that I'm neither a native English speaker nor a teacher.