When Justin Henry was Oscar nominated for the Best Supporting Actor Academy Award, Henry at age 8 became the youngest ever person to be nominated for this award as well as the youngest ever Oscar nominee in any category, a record which still stands today [August 2012].
When Billy wakes Ted the morning after the separation there is a yellow Trimline phone on the bedside table. Later that morning when Ted calls home from the office there is now a beige Princess style phone sitting on the bed.
Joanna Kramer wins custody of Billy. However, when she comes to pick him up, she tells Ted she decided to let him keep Billy. A teary Joanna goes up to see Billy, as Ted tells her she looks "terrific".