Dax Shepard appeared as one of Kristen Bell's would-be suitors. After this film, Shepard and Bell married.
People throwing coins into the Fontana di Trevi, the reputed Fountain of Love in Rome to have their wishes granted in matters of the heart, is true. In fact, it is an offense to try to steal coins from the fountain because it is the equivalence of stealing other people's wishes.
A few months into their relationship, Dax Shepard (Gale) and Kristen Bell (Beth) were riding around on a motorcycle and Bell's leg got burned. During the scenes in which Beth was in the fountain, under her dress was a garbage bag to protect her wound.
In the film, Beth is 29 and two years older than Nick, who is 27. In real life, Kristen Bell is seven and a half years younger than Josh Duhamel.
After her return from Rome, Beth receives a phone call from Joan informing her that she is "front page news," due to her climbing into the Fountain of Love. A cutaway shows a newspaper with the headline "Stupidissima." This translates not simply as "stupid," but rather as "the pinnacle of stupidity."