Mandy Moore is the youngest actor in the main cast.

Mandy Moore won her role after an audition suggested by writer Dan Fogelman, whom she knew from collaborating with on Tangled.

The wall art hanging in Kate's living room is the same as a wall hanging in Jules's living room in Cougar Town.

In the pool scene in episode 4, a boy can be seen "doing the whip" dance and "dabbing". This is unlikely to have been a dance move in the past.

Ron Cephas-Jones is father to Jasmin Cephas-Jones, the original Peggy Schuyler/Maria Reynolds of Broadway sensation "Hamilton."

Ken Olin (Executive Producer) and Timothy Busfield (Director - S1, Ep11) worked together on the late 80s hit series "Thirtysomething". Ken's character was Michael Steadman and Timothy had the role of Elliot Weston.

When Jack shirtless, he appears to have a shaved chest. That is in fashion now, but a blue collar boy from Pitttsburgh in the 1980's would not be caught dead with a shaved chest.

Spoilers

The trivia items below may give away important plot points.

There are a few hints in the pilot that Kevin and Kate are twins and that Randall is their brother. For example, in the scene where Randall gets an email saying that they found his biological father, an email entitled "It's Our Birthday Bro" can be seen in his inbox from Kevin.

In the show, Mandy Moore plays Chrissy Metz's mother. In reality, Chrissy is 4 years older than Mandy

Kevin's ex girlfriend, Sloane, also plays the sales woman from the AT&T Wireless commercials.

As of Memphis (S1 E16), Jack is the only main character to appear in every episode.

When Dr. Katowski is in the grocery store you can see Cinamon Toast Crunch on the shelf. This takes place in 1980 while Cinamon Toast Crunch came out in 1984.