LOS ANGELES (thefutoncritic.com) -- In the fall's biggest schedule revamp yet, The WB announced changes to its Monday, Wednesday, Friday and Sunday programming this afternoon.

Fridays will see the biggest upheaval as beginning October 21, "Twins" will move to 9:30/8:30c following "Reba" with back-to-back episodes of "What I Like About You" leading off the night at 8:00/7:00c. "Living With Fran," the previous 9:30/8:30c time period holder, will head to hiatus.

The same goes for Sunday nights as starting this weekend, repeats of "Supernatural" will take over the 9:00/8:00c hour from "Blue Collar TV," which will also head to hiatus.

Meanwhile, the network will swap the first-run and repeat airings of "Related" beginning October 31. Said date will see new episodes airing on Mondays at 9:00/8:00c while encores will run Wednesdays at 9:00/8:00c starting November 2.

Overall, only the WB's Tuesday and Thursday lineups will remain unchanged. To review, here's a breakdown of all the affected nights:

Fridays (as of October 21)
8:00/7:00c - "What I Like About You"
8:30/7:30c - "What I Like About You" (Repeats)
9:00/8:00c - "Reba"
9:30/8:30c - "Twins" (New Time Period)

Sundays (as of October 23)
5:00/4:00c - "Charmed" (Repeats)
6:00/5:00c - "What I Like About You" (Easy View)
6:30/5:30c - "Twins" (Easy View)
7:00/6:00c - "Reba: Beginnings" (Repeats)
7:30/6:30c - "Reba: Beginnings" (Repeats)
8:00/7:00c - "Charmed"
9:00/8:00c - "Supernatural" (Repeats)

Mondays (as of October 31)
8:00/7:00c - "7th Heaven"
9:00/8:00c - "Related" (New Time Period)

Wednesdays (as of November 2)
8:00/7:00c - "One Tree Hill"
9:00/8:00c - "Related" (Repeats)

Production on "Living With Fran" and "Blue Collar TV's" 13-episode orders this season will continue with both expected to return at some point next year.