Ah yes -- it's always the trombones.
When I marched at NC State, when we played our Big Four rivals (UNC, Duke, and Wake Forest) at home, we'd spell out their name and play their fight song. The band director said it'd probably be the only time they heard it -- we marched 175 (all male volunteers -- we added the ladies a few years later) and the others had only music majors (maybe 80-100). And the difference in teams during that era.
Anyway -- we were playing Duke and the 'bones were in charge of forming the "D" and you know where this is going. IN PRACTICE about 8 bars into the Duke fight song, the trombones changed the "D" into a "P". The band directors almost fell off the band tower. After they stop laughing and let the rest of the band in on our joke, we were STERNLY warned -- DON'T DO THIS AT THE GAME! Of course we didn't, but I don't thing any of us finished playing that fight song we were laughing so hard at what might have been.