When Lucy's Dad is talking to Lucy in the hospital, a picture of Britney Spears can be seen on a copy of USA Today that a man is reading in the waiting room.
No Coca-Cola products are ever used. Instead, Pepsi products are featured prominently, e.g. Mimi drinks from a Pepsi can in the hotel room after their karaoke win. Britney Spears, of course, endorses Pepsi-Cola.
At one point in the movie, the girls sing "Bye Bye Bye," which was a hit song by N'Sync. This was an inside joke referencing the well-publicized romance between N'Sync member Justin Timberlake and Britney Spears.
Dan Aykroyd created a detailed back-story for his character and his life in the navy. He even had a friend draw a navy tattoo on his arm (which can be seen in the scene where he is working on the car in the garage).
During the celebration scene in hotel room in New Orleans, the song that is playing on the radio which the girls danced to is entitled "Crazy Love" by Boomkat, A.K.A. Taryn Manning.
Anson Mount was originally reluctant to play Ben, but was encouraged by Robert De Niro, with whom he was working at the time on City by the Sea, who turned out to be a huge Spears fan. They went over scenes on break from "Sea", with Mount reading his role and De Niro reading Britney's.
When Lucy gets out of the shower in the first hotel room, a bottle of Herbal Essences shampoo is visible inside the shower. Britney Spears endorses Herbal Essences shampoo.
Bowling For Soup, the band who features in the film and have 3 songs in the film, belong to Spears' record company, Jive Records, as do *Nsync (the band featuring Spears' then boyfriend Justin Timberlake) who also have a song that features in the film.
The Britney Spears songs in the film all went on to become singles and were featured on her third album, "Britney", which was released shortly before the film.