From Bulbapedia, the community-driven Pokémon encyclopedia.
The following lists the changes to the possible Shadow Pokémon used by Team GO Rocket Grunts. The listings are grouped in chronological order based on the date the updates occurred.
July 22, 2019
August 1, 2019
On August 1, 2019, Team GO Rocket Grunts began using Shadow Pokémon from the Poliwag, Grimer, Drowzee, Cubone, Scyther, Magikarp, and Houndour families. On August 8, 2019, Grunts also began using Shadow Pokémon from the Ralts family, resulting in a slight change to some of their rosters.
Prior to August 8, 2019
Prior to the release of Shadow Ralts's evolutionary line on August 8, the following Grunts had these Pokémon instead.
September 5, 2019
On September 5, 2019, Team GO Rocket Grunts began using Shadow Venonat, Oddish, Psyduck, Growlithe, Abra, Hitmonchan, Larvitar, and Turtwig along with some of their evolutions.
October 17, 2019
In conjunction with the Halloween event starting on October 17, 2019, Team GO Rocket Grunts began using Shadow Weedle, Electabuzz, Magmar, Lapras, Mareep, Seedot, Sableye, Trapinch, Cacnea, Shuppet, and Duskull along with some of their evolutions.
November 7, 2019
In conjunction with the debut of Team GO Rocket Leaders, new Shadow Pokémon began appearing in the Team GO Rocket Grunts' teams: Sandshrew, Bellsprout, Magnemite, Porygon, and Wobbuffet along with some of their evolutions.
Pokémon GO Holidays 2019
An Ice-type specialist was temporarily added to the existing pool from December 24, 2019 to January 2, 2020, marking the debut of the Shadow Delibird and Snover families.
February 3, 2020
July 10, 2020
GO Fest 2020, Day 2