A “game changer” means something that “changes the game.” It does not mean a change of game meats, but there are jokes.
   
“I’m working on a device for turning rabbit into grouse and pheasant into venison. It could be a real game changer” was posted on Twitter by Russell on November 27, 2013. “Just switched from eating venison to pheasant. Absolute game changer” was posted on Twitter by Darren Walsh Puns on March 18, 2016.
   
“I have made the switch from Pheasant to Venison. It’s been an absolute game changer!” was posted on Reddit—Dadjokes on August 23, 2019. “I’ve recently switched from eating venison to eating pheasant. Absolute game changer” was posted on Twitter by The Dad Joke Man on June 5, 2020.
 
     
Merriam-Webster Dictionary
game changer noun
: a newly introduced element or factor that changes an existing situation or activity in a significant way
 
Twitter
Finn
@nofunfinn
Just had wild venison for the first time. From Maine. Cooked by my dad. Game-changer.
6:25 PM · Dec 23, 2009·Twitter Web Client
   
Twitter
AJ Beaulieu
@jdot6
Small preview of ‘the game changer’. Venison, bison, and beef patty dusted wit smoked paprika, garlic… http://instagram.com/p/ZWr6H6xh3x/
9:42 PM · May 15, 2013·Instagram
   
Twitter
Russell
@rustyhancox
I’m working on a device for turning rabbit into grouse and pheasant into venison.
It could be a real game changer.
#1PUN
8:04 AM · Nov 27, 2013·Twitter for Android
   
Twitter
Drip Baeless
@RickNossi
Oh no, there’s a burger at this restaurant called a game changer made of bison and venison…that’s a real #GameChanger
5:28 PM · Jan 2, 2014·Twitter for iPhone
     
Twitter
Michael Hogan
@michaelhogan
Thinking of swapping my venison for a pheasant. This could be a game-changer
10:14 AM · Dec 7, 2014·Twitter Web Client
 
Twitter
Andy Lulham
@LulhAndy
Replying to @SpinCycleMag
@SpinCycleMag I once decided I preferred venison to grouse - that was a game changer…
12:56 PM · Feb 17, 2014·Twitter Web Client
   
Twitter
Simon Whiteside
@cyberdonkey
“Waiter I ordered pheasant but you’ve brought me venison!”
“ Yes sir our Chef is a real game changer”
3:18 AM · Nov 24, 2015 from Brent, London·Tweetbot for iΟS
 
Twitter
Simon Varwell
@simonvarwell
I’ve just invented a machine that turns venison and partridge dishes into rabbit and grouse.
It’ll be a game changer.
3:32 PM · Dec 10, 2015·Echofon
   
Twitter
Darren Walsh Puns
@DarrenWalshPuns
Just switched from eating venison to pheasant.
Absolute game changer
10:42 AM · Mar 18, 2016·Twitter for iPhone
   
Twitter
Reader’s Digest Asia
@rdasia
Time for a Laugh
“I’ve just switched from venison to pheasant. Absolute game-changer.” – Comedian Darren Walsh
12:30 AM · Jun 7, 2017·Hootsuite
 
Reddit—Dadjokes
Posted by u/Stoatwobbler August 23, 2019
I have made the switch from Pheasant to Venison
It’s been an absolute game changer!
 
Twitter
The Dad Joke Man
@DadJokeMan
I’ve recently switched from eating venison to eating pheasant.
Absolute game changer.
9:56 AM · Jun 5, 2020·Twitter for iPhone