All are from my personal memories and experience, and all fun in its own way, even if only in recollection.
1. Your stand partner says hi, sits down and takes off his shoes.
2. The conductor walks on stage on concert night - and he's forgotten both his music scores and his baton.
3. In the first sectional rehearsal, your section principal walks into the room and says, "Wait a couple of minutes, ok, my wife is looking for my viola."
4. In full rehearsal, the conductor tells the first violins, "Don't worry if some of you are flat - some of you will be sharp, it'll all work out."
5. A cellist has cellophane tape on his strings - at the area where the bow touches the strings - they don't call it cellophane for no reason, eh.
6. The conductor screams at the second violins, "Why are you playing louder?!!!" and a freaked out Principal whispers, "Because there's a crescendo."
7. The percussionist misreads the score in Orff's Carmina Burana, mistakenly playing a tambourine for the tam-tam part, not knowing that tam-tam = the gong.
8. Orchestral conflicts take a turn for the worse when one violinist bites another.
9. The violinist near you sits down, opens his case and goes, "Oh crap", realizing that he's brought the case, but left the violin at home.
10. The violist conductor goes, "What's two bars before bar 100?" And yours truly replies, "99!" When a guest violist is later told the story, he doesn't get it, and starts counting bars with his fingers.