Yes, Monica Geller did have a romantic involvement with Ethan, who was 17 years old.
Monica and Ethan's Relationship
During an episode of Friends, Monica engages in a relationship with Ethan. It is revealed that Ethan is 17 years old, which causes Monica significant concern regarding the legal implications of their encounter. Their interaction was a notable plot point in the episode, highlighting Monica's anxieties about the age difference and potential legal repercussions.
The Age of Consent Discussion
Monica expresses worry that her actions might classify her as a felon after sleeping with Ethan. This concern stems from the varying age of consent laws. While the show was filmed in California, where the age of consent is 18, the series itself is set in New York, where the age of consent was 17 at the time. Monica's internal struggle and uncertainty about the legality of their relationship ("might be a felon"; "quite not sure and hopes that she is not") underscored the uncomfortable reality of their age gap.