This furry fiend combines the best Zombie Pets in the game. He's got everything from Zombie chickens to walrus riders to robotic sharks! Pet-themed Superpowers like Dolphinado and Frozen Tundra help his deadly zoo finish the job.
With
Brain Freeze has the most pet zombies of all zombie heroes, so it's a good idea to use him in pet decks. The Cat Lady will get strength boost from playing pet fighters and the Zookeeper will help you boost the pets up, making them a powerful army.
He is also the hero who has the second most Imp zombies, with not only the initial Sneaky Imp zombies, but also Loudmouth, Vimpire, and Kangaroo Rider, allowing him to use an Imp deck with great effects. The Toxic Waste Imp and the Vimpire make a dangerous combo, as Deadly will destroy any plant Vimpire hurts, and he has the Frenzy trait, thus allowing him to attack again, provided he is not destroyed in combat, and becoming more powerful. Boosting cards will also make them stronger.
Brain Freeze also has the most Amphibious zombies out of all zombie heroes, leading both the Sneaky and Beastly classes. This makes his zombies very hard to hit most of the time.
Frozen Tundra can also freeze all the plants on the ground, making most of the zombies on the ground safe in that turn, so zombies can destroy frozen plants easily. And since it is a classified as a pet superpower trick, it will benefit Cat Lady and Zookeeper.
Brain Freeze's main weakness is that he does not have many tools in order to stop rush decks similar to Template:PvZHLink as he cannot get The Chickening or Weed Spray, so Kabloom heroes can spam weaker plants and win from there. While Fire Rooster can help remove them due to its ability, it cannot stop many higher-health threats at once. Therefore, the closest he can go is to either fight fire with fire, use Deadly zombies, or remove them one by one with Locust Swarm.
Another weakness Brain Freeze has is that without the help of Imp Commander, he cannot draw cards at all. Opponent can drain his cards and win from there if he is not using an Imp deck, so Imp decks are a viable option to use with Brain Freeze if you prefer spamming zombies.
Against
Most of the time, Brain Freeze will attempt to use a bunch of pets, like Cat Lady and Zookeeper to boost them all up. Try getting rid of his pets as fast as possible, like Cat Lady. If they already got too strong, then use tricks to raise your plant's attack and health. Pet decks have one slight weakness, which is low health. Knowing this, try to whittle down all the zombies' health. If you are playing as a Kabloom hero, you can combine Sour Grapes with Sergeant Strongberry to potentially take all of his pets out at once. Just attacking Brain Freeze isn't really a good idea, as he will raise all his pet's stats, and then outnumber you with his powerful pets. Be careful when playing as Template:PvZHLink, as her superpower will boost Cat Lady and Zookeeper due to Goat being a pet.
Vimpires want to suck your chlorophyll! You'll find tons of ways to pump up your Vimpires to take over the game: Toxic Waste Imp, Imp Commander, and Loudmouth among them. Didn't draw a Vimpire? Other Imps will jump in with fake fangs!
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Pets with Cold Noses
Brain Freeze commands an entire zoo! Cat Lady and Zookeeper reward you for your aggressive swarm, while Vitamin Z and Locust Swarm punch through when the lanes fill up. Who knew Fire Roosters had cold noses?
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High Seas High Jinks
Impish shenanigans lead by Imp Commander keep the Plants off guard as you buy time for the mighty Zombot Plank Walker to enter the fray.
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Gallery
Plants vs. Zombies Wiki has a gallery for Brain Freeze (PvZH).
Brain Freeze's name is a pun on "brain freeze," which is what someone gets when they consume something cold too fast.
As of right now, it is unknown if Brain Freeze is a robot like the other yetis.
The card description of Brain Freeze's signature superpower contains a pun related to ice ("chill out"). This was previously seen in the Suburban Almanac entry for the Snow Pea in Plants vs. Zombies.
This is because it comes from his signature superpower, which cannot be shared with other heroes.
When Brain Freeze enters the battle at the beginning, the ice statue he breaks out from has the same pose resembling the one supposedly made by a Bigfoot in the famous footage taken during the Patterson-Gimlin film.
Sneaky and 
Beastly classes. His signature superpower is Frozen Tundra, which gives the 
Freeze effect to all plants on all ground lanes.
Sneaky, 
/1
.
Deadly will destroy any plant Vimpire hurts, and he has the 
Frenzy trait, thus allowing him to attack again, provided he is not destroyed in combat, and becoming more powerful. Boosting cards will also make them stronger.
Brainy
Crazy
Hearty
Sneaky