Threepeater

Threepeater shoots Peas in three directions; the lane above it, below it and the lane it's planted on. These are a handy middle-to-late game weapon, although it is best not to place them in the top or bottom rows, for they'll shoot two peas rather than their usual three. However, it is a good idea to plant them there after planting them in the middle rows.

Suburban Almanac Entry
Threepeater

Threepeater shoots peas in three lanes

Damage: normal (for each pea)

Range: three lanes

Threepeater likes reading, backgammon and long periods of immobility in the park. Threepeater enjoys going to shows, particularly modern jazz. "I'm just looking for that special someone", he says. Threepeater's favorite number is 5.

Cost: 325

Recharge: fast

Strategy
Since it fires down all three lanes whenever it sees anything in any lane, it can potentially hit zombies just as they enter the right side of the screen - well before other plants have noticed them. Its especially useful in conjunction with the Torchwood and on pool levels, since two Threepeaters in the second and fifth rows (both touching the sides of the pool) can cover all six lanes on a pool level.

Threepeaters have somewhat inaccurate animations and can actually hit zombies right above or below them. Because of this Threepeaters work better with torchwood than the animation might suggest: if a Torchwood is planted directly above or below the Threepeater, the Threepeater will shoot fireballs directly out of its top or bottom head (respectively) without the peas even touching the Torchwood. Likewise, if a Torchwood is planted in the row above or below a Threepeater but one column ahead of it, the Threepeater's peas will turn into fireballs despite not having fully moved into the row and not having gone through the Torchwood.

Advantage

 * 1) Saves spot instead of 3 Peashooters.
 * 2) Only need one pumpkin to protect unlike 3 peashooters which need 3 pumpkins.
 * 3) Require only one Lilypad & Flower Pot.
 * 4) Can be combined with garlic like other plants who can attack outside of it's lane.

Disadvantage

 * 1) More expensive than three Peashooters (excluding if you count Lilypad and Pot).
 * 2) Only require one zombie to eat and when a zombie eats it, all three lane became vulnerable.
 * 3) Wastes money when planted on the wrong place (top and bottom lane).
 * 4) Too expensive that you probably lose one or two lawn mowers before you can plant one (except if you play with potato mine).

I, Zombie
Threepeaters are encountered in various I, Zombie levels, including I, Zombie Endless. Like the Starfruit and Magnet-shroom the Threepeater is one of the few plants capable of affected other lanes than the one its planted in. This forces the player to consider other lanes besides the one currently being assaulted. For example: an Imp about to walk down a seemingly undefended lane might still get killed by a Threepeater, wasting sun.

Trivia

 * If there is a Threepeater on the top or bottom row, the top or bottom head (respectively) does not have its firing animation play, as it cannot fire outside the screen.
 * If you play I, Zombie with a Threepeater at the top or bottom row, the top or bottom head respectively won't move at all as the paper cut-out plants will only move if there is a zombie.
 * The Threepeater's three heads bounce at different speeds. The bottom head bounces the slowest, while the middle head has an average speed, and the top head bounces the fastest.
 * Each head also has a different number of leaves on the back; the bottom one has one leaf, the middle one two, and the top one three.
 * The Threepeater is the most expensive non-upgrade plant in the game, costing 325 Sun.
 * The Threepeater is the only plant with three heads.
 * In the Xbox Trailer, when the person says, "You feel always safe", only Threepeaters are on your lawn.
 * The Threepeater, the Starfruit, the Cattail, the Cob Cannon, and the Gloom-shroom are the only plants that can fire outside the lane it is planted on.
 * If you observe carefully, you will see 3 peas coming out of the middle head only.
 * The Threepeater is obtained during a pool level and thus, it is equal to three Peashooters and one Lily Pad.
 * Threepeater is one of the twelve plants that appear in the seed selection screen after you get the Grave Buster on the online version, the others are: Ice-shroom, Lily Pad, Potato Mine, Doom-shroom, Tangle Kelp, Jalapeno, Spikeweed, Torchwood, Tall-nut, Cactus and Blover.
 * The Lawn is flat yet the top head could hit the lane on the left and the bottom head could hit the lane on the right even though the heads are above and below the center head.
 * When the Threepeater shoots, the first pea goes forward as per normal, but the top and bottom peas come out from the middle then stay on that lane as if there is a swerve or curl.
 * Threepeater is a portmanteau of the words "three", in refernece to the number of heads, and "repeater", in reference to the number of peas it shoots.