“Brooklyn Nine-Nine” said goodbye to Chelsea Peretti on Thursday, and fans were apparently too sad to watch. The former Fox comedy slipped 20 percent in TV ratings from last week’s preliminary ratings.

It’s worth noting here the prior “Brooklyn” adjusted down in final Nielsen numbers, so the eventual week-to-week decline could prove less.

NBC’s “Will & Grace” returned afterward when that sitcom bested its own fall finale. “The Big Bang Theory” came back last night, and CBS beat up on the rest of broadcast.

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CBS was first in ratings with a 1.4 rating/6 share in the advertiser-coveted 18-49 demographic and in total viewers with an average of 8.5 million, according to initial numbers. “Big Bang” at 8 p.m. scored a 2.4/11 and 13.5 million viewers. At 8:30, “Young Sheldon” earned a 1.9/8 and 11.6 million viewers. “Mom” at 9 posted a 1.3/6 and 8.7 million viewers. At 9:30, “Fam” had a 1.0/4 and 6.1 million viewers. “S.W.A.T.” at 10 got a 0.9/4 and 5.7 million viewers.

ABC was second in ratings with a 1.1 and in viewers with 5.1 million. “Grey’s Anatomy” at 8 landed a 1.7/8 and 7.2 million viewers. “A Million Little Things” at 9 had a 1.1/5 and 5.3 million viewers. At 10, “How to Get Away With Murder” got a 0.6/3 and 2.6 million viewers.

NBC was third in ratings with a 0.9 and in viewers with 4.1 million. “The Titan Games” at 8 had a 1.1/5 and 4.6 million viewers. At 9, “Brooklyn” managed a 0.8/4 and 2.8 million viewers. “Will & Grace” at 9:30 got a 0.8/3 and 3.1 million viewers. “Law & Order: SVU” at 10 received a 0.9/4 and 4.6 million viewers.

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Fox was fourth in ratings with a 0.7 and in viewers with 2.8 million. “Gotham” at 8 had a 0.7/3 and 2.4 million viewers. At 9, “The Orville” got a 0.7/3 and 3.1 million viewers.

Univision was fifth in ratings with a 0.5/2 and in viewers with 1.4 million.

Telemundo was sixth in ratings with a 0.4/2 and seventh in viewers with 1.1 million.

The CW was seventh in ratings with a 0.3/2 and sixth in viewers with 1.2 million. “Supernatural” at 8 had a 0.4/2 and 1.4 million viewers. At 9, “Legacies” got a 0.3/1 and 1 million viewers.