For the first two seasons, Cam and Mitchell's daughter, Lily, is played by a set of twin girls named 'Ella Hiller' and 'Jaden Hiller'. They are not given an on-screen credit.
In a 2010 interview with "Out" Magazine, Jesse Tyler Ferguson said that the running joke that Jay kept "forgetting" that his son, Mitchell, is gay (and Mitchell had to come out to his father repeatedly) is drawn from Ferguson's real life - he had to come out to his real father three different times over many years before his father actually believed it. When Ferguson told the show's writers this story, they found it very funny and decided to add it to Mitchell's backstory.
Phil's birthday is either on April 3rd or 30th (US release dates of the original iPads). This is due to a joke in which Phil says 'The iPad comes out on my actual birthday, it's like Steve Jobs and God got together to say "We love you, Phil"'
The license plate on Cameron and Mitchell's car (2GAT123) is the same as Larry David's on Curb Your Enthusiasm. It is also the license plate on the "Beverly Hills Cop" car.
Britney Spears was reportedly offered a role in the middle of Season 3, but by the time producers heard from her people, they had the rest of the season already planned.
Nicole by O.P.I. has a line of nail polishes that are marketed and advertised in print as "inspired by TV's Modern Family". Their print ads feature Julie Bowen, Ty Burrell, Sarah Hyland, Ariel Winter and Nolan Gould in a family portrait group image.