Girl (not Lady) is the female Whippet that Niles Crane adopts after his trial separation from longtime wife Maris Crane. The dog is very slim and frail-looking not unlike most Whippets, however she is extremely
reclusive and does not acknowledge any commands given to her by her master, such as in "Death and the Dog" she refused to approach nor be playful with Eddie, requiring Niles to pick her up and do it for her.
There have been many observations that Girl bears a strong resemblance to Maris in both physical appearance and in attitude, despite being a canine. She has a snobbish demeanor similar to Maris such as when Niles wanted to pet her at the kennel, she would have none of it and Martin Crane refers to her as a "four-legged Maris", referring to the fact that it "acts like Maris, barks like Maris, and aside from the fact that it eats now and then they're dead ringers".
When Niles finally found his dream home he was notified that there was a strict no cats or dogs policy enforced so Niles had to give Lady up to another family.