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2.
When you are a sophomore or a higher grade and you meet freshmen who are obvious that they are freshmen. The freshmen are like pets because they're not used to being in high school like the sophomores and upperclassmen have experienced.
girl 1: look at those freshmen sitting at our table.

girl 2: yeah but they're my pet freshmen
by look at that chick January 11, 2013
 
1.
When an upper classman (such as a junior or a senior) adopts the new addition to the school, a freshman. Pet freshmans are a joy to have and can help you through sticky situations. Upper classman usually argue over who's pet freshman is better.
ex1
Junior (Miranda): CALLIE, MY AMAZING PET-FRESHMAN I HOPE THIS COUNTS AS AN EXTRA-AWESOME BIRTHDAY GIFT! I mean getting put in an example for urban dictionary? whats more badass then that?
Pet-Freshman (Callie): OMG MIRANDA YOU'RE SUCH AN AWESOME JUNIOR ITS RIDICULOUS! THANK YOU SOOOO MUCH!

ex2
Senior (Michael): Man, my stupid pet freshman blows. i should have chosen someone cool like Callie.
Pet-Freshman (Conor): But Michael i tried so-ooo penny! *runs away*

ex3
Junior/Senior: Pet Freshman! Go kill the other pet freshman!
Pet Freshman: KAH-MAY-HA-MAY-HAAAA! *pet freshman dies*
by mp054 March 19, 2010