Brain

In the Plants vs. Zombies series, brains are the favorite food of the zombies and the incentive for zombies attacking the player. In Plants vs. Zombies: Garden Warfare and Versus Mode, they are the zombie equivalent of sun.

Plants vs. Zombies
In Plants vs. Zombies, the zombies eat brains, which is why the player's house is being invaded. They also appear in the mini-game Zombiquarium, where they are used to feed Snorkel Zombies so they do not die. The I, Zombie Puzzle Mode levels have the player placing zombies who must eat the brains at the end of every lane which are worth one silver coin ($10) each. As previously mentioned, they are the zombie equivalent of sun in Versus Mode. A brain is also featured in the song Zombies on Your Lawn, and is used as a pointer for the lyrics. In parts of the game, some zombies can be seen showing brains on pieces of their clothing or equipment. For example, the Zombie Bobsled Team has a brain picture on the front of their bobsled and the words "Brains or Bust" written on the side. The Dolphin Rider Zombie's Speedo-type outfit has a picture of a brain on it, the Snorkel Zombie has a shirt with the legend "I ♥ Brains," and the Flag Zombie carries a red flag with a picture of a brain on it. One of the Chinese zombies in the bottom of the achievement page has a takeout box with a picture of brains on the side.

Additionally, a game over message in green blood saying "THE ZOMBIES ATE YOUR BRAINS!" will appear along with a "NOOOOOOOOOOOOOOOOOOOOOOOO!" if the zombies get inside the player's house.

Versus Mode
The brains are given a vital role in the Xbox Live Arcade and Nintendo DS versions in Versus Mode as the zombies' equivalent of sun. They are used to place zombies in a similar manner to placing plants in order to attack the opponent's lawn and try to eat their brains. Much like sun, brains will fall from the sky anywhere in the three lanes controlled by the player who is playing as zombies, and will be produced from Zombie Gravestones at the same rate that Sunflowers produce sun.

Brainball
In Plants vs. Zombies Adventures, brains serve a big purpose in Brainball. They are used as the scoring system. Players have to hide brains in their buildings and get brains from other people's buildings. To do that, they have to send zombies and win the attack. Brains do not count for the score if they are not stored in buildings. If the player attacks another player's town and gets brains, then the Brains will automatically be placed in the Player's Town.

Plants vs. Zombies 2
Brains do not have any usage in Plants vs. Zombies 2, unlike its predecessor. Like other games, when the zombies enter the player's house, a message says "THE ZOMBIES ATE YOUR BRAINS!," and an image of a brain on a silver plate with a bite taken out of it is shown. If the player taps on the brain, it will squiggle around and make a squishy sound. The same brain also appears at the bottom of the credits. A brain also appears on one of Jester Zombie's plates on his costume during the Thanksgiving Food Fight Piñata Parties.

Plants vs. Zombies: Garden Warfare
Unlike all previous games, in Plants vs. Zombies: Garden Warfare, the objective of the zombies are not eating the player's brain. Brains only appear on the zombie side of Boss Mode. It serves a similar purpose as sun, as in Zomboss Boss Mode brains drop from the sky and need to be collected in order to build healing, spotting, and reviving stations, or make cone bombardments to support the team. Each falling brain collected worth 25 brains.

Audio
The screaming sound that can be heard when the player loses.

General

 * The green blood on the game over screen could be one of the main reasons why Plants vs. Zombies is rated E10+ by the ESRB.

Specific to Plants vs. Zombies

 * In Zombiquarium, one brain costs five sun. This is odd because in Versus Mode, one gives five times the amount of power one costs. Of course, these are in two completely unrelated game modes and maybe a brain costs 5 sun and it gives 25 sun.
 * Several zombies use pictures of brains on items they use or carry, like the Zombie Bobsled Team, which has a brain on their bobsled, or the brain on the Flag Zombie's flag.
 * The clouds in the HD version of Plants vs. Zombies iPad in the Roof levels are shaped like brains.
 * There are also brain clouds during the song Stop Zombie Mouth! in the part where an Imp flies with a tube of toothpaste, leaving a trail of toothpaste.

Specific to Plants vs. Zombies 2

 * If the player touches the picture of the brain after losing, it will make a "squish" sound. It also squishes in game.
 * Despite the zombies are trying to eat the player's brain, Jester Zombies in Food Fight parties actually hold a pan with a brain (in its costume). However, the brain might be fake.

Specific to Plants vs. Zombies: Garden Warfare

 * This is the only game where the zombies do not try to eat the player's brains.
 * However, on Team Vanquish Mode, when the plants reach 40 vanquishes, it is possible for Dr. Zomboss to say: "The Plants only need 10! Don't you want brains?"
 * This could mean that Dr. Zomboss has a supply of brains he is using to motivate the zombies to win.