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. When Beth was in the fountain, under her dress was a garbage bag to protect Bell's wound.
Jon Heder's character, a goth street magician, was a parody of famous illusionist Criss Angel (in both looks and magic tricks performed).
After she returns 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".