While some people had Russian tests and statistics problem sets due this Halloween, others got to dress up — for credit.

This week students have donned dorm-made Where’s Waldo? costumes to get extensions on papers, while others have gone around as psychological disorders, showing once again that even Yale knows when to take time off to play.

For Kristi Lockhart’s “Abnormal Psychology” class, students were able to get five extra credit points if they came dressed up as something relevant to the class.

Twins were the most common. Several students showed up as fraternal and identical twins, as well as the Ginean twins, an infamous set of quadruplets named Nora, Iris, Hester, and Myra, who dressed alike. Students wore one of the letters N, I, M, or H to represent the twins.

One student came as a Freudian slip — in a slip. Other students came as regression, dressed as children, while others portrayed identification by sticking their heads through cardboard licenses. And then there was a grandiose delusion.

Wearing a white coat, one girl went as Hippocrates, bringing four liquids with her to represent the four humours: phlegm, yellow bile, black bile and blood.

One boy came as penis envy. He wore a piece of paper on his shirt with an arrow pointing to his crotch with the word “jealous” written above the arrow.

In his small seminar class “Law and Politics in South Asia,” Matthew Nelson also rewarded students who dared to embarrass themselves.

“Our teacher said he’d give us an extension on our papers if we came to class in costume on Halloween,” Julia Holleman ’05 said.

Another student in the class, Arjun Rajagopal ’03, said the decision whether to work or take advantage of the holiday was an easy one.

“The choice was either to turn in a prose outline or come dressed up,” Rajagopal said. “We got a couple days extra in turn for providing some amusement.”

“One guy came as Jesse Helms, and a few other people didn’t come in costumes because they turned in their papers,” Holleman said. But the rest of the students coordinated to pull off a living Where’s Waldo? game.

Holleman said everyone wore red long-sleeved shirts with masking tape, as well as blue jeans and Waldo-type hats. The only difference between them and Rajagopal, the “true Waldo,” was that Rajagopal wore glasses.

Rajagopal said Nelson probably was not expecting the turnout.

“I don’t know when he said it. I think he was pleasantly surprised when three quarters of the class showed up [in costume],” Rajagopal said.