The character of Mary Connell (Nikki Cox) was originally written to be a high-class hooker, and was filmed that way in the pilot. Mary is seen several times with a "date" and the dialog is consistent with that of a call-girl. After filming, the character was re-envisioned as the hotel's "Special Event Director". It's only in Danny's (Josh Duhamel) voice-over / narration, that he clarifies she isn't a hooker.
In the pilot, the character of the Bum (Mr. Bunny Shoes) is based on a real-life homeless person who parlayed his social security check into over $1.2 million, and lost most of it back.
Marsha Thomason originally auditioned for the role of Sam, using an American accent. After the audition, when the creators were told she was actually British, they called her back and asked her to read the part in her native accent. They liked her so much, that they rewrote the minor role of the pit boss called the "Iceman", who was Danny's Godfather, as the "Ice Queen", Nessa Holt, and gave her the role.
The character of Delinda Deline (Molly Sims) was originally envisioned as a minor character who only made occasional appearances. Producers were so impressed with Molly's acting, that they made her a primary character.
The mystery surrounding the death of Mary and Danny's friend Greg was originally intended to be a season-long story. However, NBC asked the show to make more self-contained episodes, so Greg's death was wrapped up quickly early in the season.