One other interesting example: Mahler's first symphony, third movement (https://www.youtube.com/watch?v=U5A5tFyXQio https://www.youtube.com/watch?v=U5A5tFyXQio)

One other interesting example: Mahler's first symphony, third movement (https://www.youtube.com/watch?v=U5A5tFyXQio https://www.youtube.com/watch?v=U5A5tFyXQio) which incorporates a minor-ized version of the classic (major) Frere Jacques tune as a motif.