Old School
When I joined policing, the "blanking new guy" caught every sorry assignment. If it was a crime scene that was reeking, you had the crime scene access log so you could smell it. You were not allowed to use the elevator, but had to take the stairs…that one was from my old Chief himself.
You had to get a few embarrassments under your belt and before you knew it, you were somewhat accepted. Some say that you are not the "real police" until you've had your first big bar fight, pursuit (both foot and vehicle), or first trip to the emergency room. It matters not; it is all about "firsts."
Somehow or other I and thousands like me made it through the rookie gauntlet and lived to tell about it. Looking back, none of us would trade these events, and we even laugh about them. And most fully participate in them today, for it is tradition.
Today
Nowadays, the Field Training Officer (FTO) program takes care of most of the "firsts." Often by the time a recruit has completed the multitude of weeks with an FTO, most of the introductions to the watch or precinct are taken care of. So fellow officers feel the need to make their own "introductions."
I must remind you that officers are not picking on you or bullying, but carrying on their—and soon to be your—traditions. What can be a little joke could be a lead-in for a teaching point. Often, life's lessons are the ones we take the hardest.
For the old guys here, if you insist on this, make sure there is a valid life lesson or teaching point for this gesture. Yes, in police work it is much akin to when your father taught you to ride a bicycle; you got scuffed up but you learned.
Humor
The recruit must understand that this is also a test of your sense of humor more often than your heart. Cops are often the most jaded people I have ever known, but they will laugh at themselves, especially when nobody else finds it humorous. This is a great quality to have.
Now, if the lines of proper decorum are crossed and you are subjected to cruelty or something illegal, contact your supervisor. But, when you find out that your car was set up (all the emergency equipment comes on when you turn the key), stop, laugh, and know that one day you will be subjecting a younger colleague to such silliness.
Train hard but have fun.