"That's a rule in the business. No tongue. You can't really get into it, otherwise, it's weird. I think that particular scene made his (Adam Brody) girlfriend jealous. There were issues"

In this quote, Rachel Bilson talks about the subtleties and boundaries associated with on-screen kissing, especially in the show business. The expression "That's a rule in business. No tongue", indicates that there is an unwritten code of conduct amongst actors when shooting kissing scenes. The guideline against making use of tongue recommends an effort to keep a level of professionalism and comfort in between co-stars. It acknowledges the intimate nature of kissing scenes, which, while they may appear authentic to the audience, include stars who are merely performing their functions. This guideline most likely exists to avoid any crossing of individual limits, preserve professionalism, and prevent producing tension or discomfort either on set or in the actors' personal lives.

Bilson even more explains, "You can't really get into it, otherwise, it's odd". This suggests that adding excessive realism or personal feeling to a staged kiss might complicate the working relationship between actors. It might blur the lines in between acting and real-life emotions, making the procedure uncomfortable or "weird" for those included. It likewise suggests that the actors' goal is to convincingly portray romantic chemistry without letting that extend beyond their characters.

The last part of the quote, "I think that specific scene made his (Adam Brody) girlfriend envious. There were concerns", adds another layer of intricacy, indicating that even with these professional borders, emotions and real-life relationships can still be affected. Despite the adherence to industry norms, Brody's sweetheart reportedly felt uncomfortable with the scene, resulting in "issues". This underscores how the representation of on-screen love can occasionally affect real-life relationships, regardless of efforts to preserve professionalism. It highlights the often difficult balance actors should strike between their on-screen work and their off-screen lives, as well as the potential for misunderstandings to occur even when limits are appreciated.