Chihuahua-Dachshund sisters, Princess and Diamond, jumped over each other and licked the fingers of those considering adopting the 4-month old puppies. The duo, foster puppies from Animal Care & Control, were just two of thousands of dogs, cats and rabbits on hand for the city's free Maddie's Pet Adoption Days in Union Square over the weekend.

More than 3,500 animals found homes in the largest adoption event, hosted by the Mayor's Alliance for NYC's Animals, said Jane Hoffman, the group's founder and president. More than 90 animal shelters and rescue groups brought their furry friends to Union Square on Saturday and Sunday.

Roommates Martha Souder and Rachel Plast, both 23, moved to the city together three months ago from Wisconsin.

"We're looking for a new addition to our New York family," said Souder, who held Diamond inside the AC&C's adoption truck. "We wanted to come see if we could find the right dog."

All adoption fees have been waived for the event and are subsidized by Maddie's Fund, a California-based organization that promotes the idea of a no-kill country. Similar events are planned in eight other states.

In fact, the shelters receive more money per adoption from Maddie's Fund than they normally do, Hoffman said.

"I think it brings awareness to all these animal groups and shelters. I think it's fabulous," she said. "I think the only thing is we're running out of dogs and cats and kittens, which is a good problem to have."

Francina Pena just moved to the Bronx from the Dominican Republic with her 4-year-old daughter, Emilia. Pena, 23, said they had a cat but had to leave it behind. Sunday Pena, a home attendant, brought her daughter to pick out a new friend.

"She's having a hard time adjusting," she said, after Emilia picked out a brand new kitten. "We thought it was a good idea for her to have a buddy. For her to feel not so alone.

"She fell in love with it," Pena added. "She just said 'I want that one.'"