Yes, Lisa Kudrow, who played Phoebe Buffay, was pregnant during the filming of Friends.
This real-life pregnancy was incorporated into the show's storyline. The writers decided to make Phoebe a surrogate mother for her brother Frank and his wife, Alice, carrying triplets. This allowed Kudrow's pregnancy to be visible and explained within the narrative of the show without impacting the storylines of the other characters. The writers chose surrogacy which aligned with the show's themes of family and unconventional relationships.
Therefore, the answer is definitively yes.
