I just had a bizarre thought!
Is there a note that stays the same regardless of what scale you are in??
Is there any in the Major scales or in the minor scales?
There aren't any in the major scales.
For instance, Ab Major has Bb, Eb, Ab and Db. Meanwhile, A Major has F#, C# and G#. So every note in C major that isn't flatted in Ab major is sharped in A major.
There is also the extreme example of C# major, where every note is sharped.