A junior in a leprechaun costume, complete with shoes and top-hat, hid behind a tree outside Jonathan Edwards College Thursday night waiting to be inducted into one of Yale’s senior societies.

Throughout the evening, cloaked figures descended on campus, rushing to initiation events, dropping off mysterious packages and generally drawing attention for their antics. In an email to the campus Sunday evening, Dean of Student Affairs Marichal Gentry told students to follow undergraduate regulations — which prohibit “activities that involve indecent exposure, extreme mental stress, blindfolding, confinement, assault” and several other activities — during society Tap Night on April 11.

“If you’re tapping new members, I’m counting on you to provide leadership to them, by showing them how to plan a big event and play by the rules,” Gentry said in his email. “If you are being tapped, I’m counting on you to speak up and refuse to participate if anyone asks you to break rules or laws, violate your conscience, or risk your safety.”

Gentry also said he knew “how exciting Tap Night [could] be” and hoped students would enjoy the event.

Throughout the day, students dressed as Darth Vader, Batman, Teenage Mutant Ninja Turtles and other superheroes invaded campus locations such as Commons and various dining halls, said students interviewed.

By 6 p.m., a junior girl dressed as Luigi from the popular Super Mario video games was stationed outside the York Street entrance to Davenport College, where she was stopping passersby.

“Well, I’m not really sure what I’m supposed to be doing,” she told the News. “I was told to stand here in this costume and insult Mario — so … I hate you Mario!”

A block down, a masked student sat by the steps of the University Theatre in a mock Hazmat suit. He said he was told to dress “so he doesn’t get dirty.” Next to the student sat an empty goldfish bowl, filled with pebbles and water.

“I have killed my fish Rachmaninov,” he said and did not explain further.

Another student in a similar Hazmat suit, also carrying an empty goldfish bowl, stood outside the Yale Center for British Art until a student in a black cloak and mask relieved him around 6:30 p.m.

Meanwhile, a masked and cloaked senior rushed down High Street with a two-page printed tap night schedule in hand that listed in detail who was supposed to be where, when and how they were supposed to be dressed up. She had organized a scavenger hunt for juniors about to be inducted into her society earlier that night and was now on her way to Sigma Nu to meet up with the “tapped” juniors.

The Tap Night shenanigans drew the attention of New Haven residents.

An elderly man walking along High Street stopped to gawk at a crowd of colorfully costumed girls, some in togas, some wearing wings, others with tiaras.

“Must be society Tap Night,” the man said.

Last year, Tap Night took place on April 12, 2012.