The Bug: 

You can get free snowballs in Eerie Mojang Office Party Event and retain them.

Steps to Reproduce:

1. Join Eerie Mojang Office Party Event.
2. Go into the rollercoaster ride. Try to hit the target balloons. If the counter does not appear due to a bug, proceed. To get the counter to disappear,  the counter can also disappear randomly, or even not appear at the start of the ride. If you are successfully able to complete the ride with the ride results, restart the reproduction steps.
3. Go up to the end of the ride, then dismount the minecart. Be careful not to get trapped in a nearby hole!
   • If you fail this step, you will end up in a nearby hole. There is also a final wall to cross at the end of the ride, which contains the last invisible barrier.
4. You should be standing on this corner rail:
5. Make sure you are facing this way:
6. Move forwards in the direction you are facing from step 5 until you collide with the barrier.
7. Enable Auto Jump if you have not already.
8. Turn 90 degrees clockwise. 
9. Move forwards again in the current direction you are facing.
10. Turn 90 degrees anticlockwise. 
11. Move forwards again in the current direction you are facing.
12. Turn 90 degrees anticlockwise once again. 
13. Move forwards again in the current direction you are facing until you escape the window.
14. At this point, you can freely move and look around.
15. Go into one of the tubes that take you to the different parts of the Mojang office in the event server. At this point, the minecart ride results should briefly appear.
16. You should have snowballs in your inventory, ready to be used everywhere on the event.

Alternate way:

1. Join Eerie Mojang Office Party Event.
2. Go into the rollercoaster ride. Try to hit the target balloons. If the counter does not appear due to a bug, proceed. To get the counter to not appear, there is a random chance.
3. Once you get past the first tunnel of creakings, proceed through the ride, and jump off midway the ride. Your character has to leave the ride and return to the ground by falling before the second tunnel of creakings appears.
4. Go into one of the tubes that take you to the different parts of the Mojang office in the event server. At this point, the minecart ride results should briefly appear.
5. You should have snowballs in your inventory, ready to be used everywhere on the event.

Please do tell me if you were affected!

Notes:

You can lose the items you have obtained in the event when you do this glitch.