Dawson Casting: Subverted and played straight. In the beginning of the series the main characters were supposed to be around 24. They were played by 22 year old Ryan Reynolds, 26 year old Richard Ruccolo and 32 year old Traylor Howard, but it looked convincing enough. In the second season, however, Reynolds was paired off with the 32 year old Suzanne Cryer as Ashley and the age difference did show.
There's some irony in the second episode of the third season, when an entire subplot was devoted to Berg being repeatedly made to feel old by a new "teenage" employee at the pizza place who was actually only three years younger than Ryan Reynolds.
Friday Night Death Slot: After ABC moved it to Friday, they tried moving it back to midweek as a two-week test to see if anyone would watch. It failed and the show was canceled.
Keep Circulating the Tapes: Finally averted, with the first season being released on DVD in April 2012, and the remaining three seasons scheduled to follow later in the year. Over a decade after the show went off the air, and long after Ryan Reynolds & Nathan Fillion have achieved greater popularity with other roles.