Think about the classes u had together.
Did any of the professors look like any pop icons??
If 2 celebrities had a baby it'd look like.... etc.?????
Think of something like that.
Then you can try and open with:
"Hey i've had a few classes with you. Oh my God! You were in my psych 101 class last fall with that professor Carter guy. This is the funniest thing... (dont forget to hook her first which is why i added the 'oh my god' and 'this is the funniest thing' statements) but i couldnt concentrate all semester because he looked like if Lady Gaga and Gary Busey had a kid it'd be him!"
...then you can always go back to him with humor saying sh1t like one day he was lecturing and you had just heard that pokerface song in the car on the radio and you kept hearing it over and over in your head as he was lecturing. etc etc.
IMO if you want to be funny with her you might as well draw from an experience you both already shared which is the fact that you've already had classes together. Think back at the classes you shared and one of those dopey proffessors has to look like someone or something that is funny. If u want cut and paste a pic of some of them. I'm good at discovering what or who random people look like. Girls will laugh at shit like that too provided your not poking fun too harshly and it is brought on at the right time in a set. In this case you can open with this technique.
also, the fact that you have already shared some time together is a great thing to draw from.
good luck bro'ski