Wrinkler

Wrinklers are leech-like creatures who can only be seen during the Grandmapocalypse (unless the game is glitched or hacked). They will appear far away from the big cookie, then slowly approach it and begin to feed on it and produce cookie particle effects similar to those produced upon clicking the big cookie. Each Wrinkler will lower your cookies per second by 5% during the feeding process. This does not affect the number of cookies you get from clicking the big cookie, because the game states that your CpS is withered, not cookies per click.

Wrinklers can be killed, or popped, by clicking on them at least three times. When one is popped, it will drop the number of cookies it has sucked over its life multiplied by 1.1. If the Halloween Seasonal Event is activated, then it also has a 5% chance of unlocking one of the 7 Halloween cookie types. If the player goes into the stats menu, it will tell how much of the current CpS has been withered, and how many Wrinklers have been popped.

The number of cookies being withered away is equal to how many wrinklers are present times 5%. If multiple Wrinklers are present, the Wither rate is increased from 5% to 10%, 15%, etc, up to a maximum of 50%. Each wrinkler considers the full wither rate to be the rate that it sucks at, not just its individual 5%, for the purposes of calculating how many cookies you receive when popped. Thus, as the number of Wrinklers grows, the amount of cookies found after popping them begins to increase quickly. A single Wrinkler gives an effective 5% boost to CpS, though the effect is not visible until the Wrinkler is popped. Because of the stacking effect, a full 10 Wrinklers give an effective rate of 6 × CpS, although once again, the benefit is not noticed until the Wrinklers are popped. If the Wrinkler has not yet reached the big cookie, it will not drop any cookies or upgrades when killed.

If you choose to end the Grandmapocalypse (using the Elder Pledge, Elder Covenant, or by selling all grandmas), all the wrinklers on the screen will pop, and they won't come again until the grandmapocalypse returns.

CPS multiplicator

To calculate the effective CpS multiplier, assuming $N$ Wrinklers present, the formula consists of: $1$ (Base factor) $- 0.05 \cdot N$ (5% withered per Wrinkler) $+ 0.05 \cdot N^2$ (each Wrinkler hoards 5% times number of Wrinklers present). This is further amplified by a flat factor of $\cdot 1.1$ (10% gain after popping) and optional $\cdot 1.05$ (5% more cookies) per Wrinklerspawn upgrade. Put together and simplified, this is this is $1 - 0.05 \cdot N + 0.05775 \cdot N^2$ with Wrinklerspawn and $1 - 0.05 \cdot N + 0.055 \cdot N^2$ without.

From the above formula, we can draw the following CPS conclusion:

No. Wrinklers	CPS Multiplier	CPS Multiplier with "Wrinklerspawn"
0	1	1
1	1.005	1.00775
2	1.12	1.131
3	1.345	1.36975
4	1.68	1.724
5	2.125	2.19375
6	2.68	2.779
7	3.345	3.47975
8	4.12	4.296
9	5.005	5.22775
10	6	6.275

Spawn Rate

Each empty Wrinkler slot has a (re-) spawn rate of 0.003% per Grandmapocalypse stage per frame (the usual framerate is 30 fps). And, from this we can draw the following:

Wrinklers Respawn Rate
Wrinklers Alive	Probability of Respawn Each Second
Wrinklers Alive	One Mind	Communal Brainsweep	Elder Pact
0	0.896%	1.784%	2.665%
1	0.807%	1.607%	2.401%
2	0.718%	1.430%	2.138%
3	0.628%	1.252%	1.872%
4	0.539%	1.074%	1.607%
5	0.449%	0.896%	1.341%
6	0.359%	0.718%	1.075%
7	0.270%	0.539%	0.806%
8	0.180%	0.359%	0.539%
9	0.090%	0.180%	0.270%

On average, it takes 18 minutes and 4 seconds for all 10 Elder Pact (speedup factor $x = 3$ ) Wrinklers to spawn, from a starting point of 0 Wrinklers. This is calculated by the sum over the inverse probabilities of occupying each slot: $\sum_{k=1}^{10} \frac{1}{x \times k \times 0.00003} \approx 32544\text{ ticks} \approx 18\text{ min }4\text{s}$ . For Communal Brainsweep, x is 2, and therefore it takes 3/2 of that time, about 27 minutes. For One mind (x=1) this is three times as long, which is about 54 minutes.
As the CPS multiplicator gain from Wrinklers depends heavily on the number of Wrinklers, but respawn time also is longest for the last Wrinklers, one should not pop single Wrinklers on demand. The last Wrinkler takes about one third of total spawn time (6 min 10s for Elder Pact, see above), while CPS multiplicator is reduced from 6.275 to 5.22775 during that time. Ten consecutive pops therefore reduce CPS by 20% for an hour. A full Wrinkler rebuild has a much stronger impact on CPS (effective multiplier 3.59), but only for 18 minutes. After that, the full 6.275 multiplicator from ten Wrinklers is active again. In other words: Extrapolating the full rebuild time to the one-by-one approach (~1 hour), rebuilding has an effective multiplier of 5.48762 over that time, while popping them in turn yields 5.22775, about 5% less. Besides that, getting all withered cookies back at once may lead faster to a CPS increase by new buildings, and is also much less time-consuming and error-prone to perform.

Upgrades

WrinlerChart — Upgrade Probability Distribution

Exploding a Wrinkler after it has begun to feed on the big cookie has a 5% chance of unlocking 1 of the 7 Halloween-themed cookie upgrades. If you have the Spooky cookies achievement, it increases to 20% chance. However, if the particular upgrade chosen at random is already unlocked, it will not unlock a new one. So on each Wrinkler explosion, the actual chance of unlocking a new cookie type is equal to $r \cdot \left(1-\frac{N}{7}\right)$ , where N is the number of upgrades already unlocked and r is the success rate (0.05 normally, 0.2 with "Spooky cookies", 0.145 with "Santa's bottomless bag", and 0.28 with both).

The expected value of Wrinkler explosions needed (without "Spooky cookies") to unlock all 7 Halloween cookie upgrades is 363. More importantly, for those who are not seeing the upgrades, the 90th percentile is more around 600 Wrinklers. After that point, you can blame your luck or lack of it.

Probabilities for Halloween-Themed Cookies
Cookies Unlocked	Probability of Appearance
Cookies Unlocked	Without "Spooky cookies"		With "Spooky cookies"		With "Santa's bottomless bag"		With both
0	5%	One in 20	20%	One in 5	14.5%	One in 7	28%	One in 3.5
1	4.29%	One in 23	17.1%	One in 6	12.4%	One in 8	24%	One in 4
2	3.57%	One in 28	14.3%	One in 7	10.4%	One in 10	20%	One in 5
3	2.86%	One in 35	11.4%	One in 9	8.29%	One in 12	16%	One in 6
4	2.14%	One in 47	8.57%	One in 12	6.21%	One in 16	12%	One in 8
5	1.43%	One in 70	5.71%	One in 18	4.14%	One in 24	8%	One in 12
6	0.714%	One in 140	2.86%	One in 35	2.07%	One in 48	4%	One in 25
Expected value for Wrinkler explosions to unlock all	363		91		125		65

A method to get all the cookie upgrades quickly is to wait for a few wrinklers to spawn, wait for an autosave ("Game Saved" popup), pop the wrinklers quickly, and - if no cookie upgrade appeared - quickly hit F5 to reload before the game is autosaved again - the wrinklers will be back and you can try popping them again.

Another way, similiar to the first, is to open mulitple tabs with wrinklers, and pop the wrinklers on each tab until you get a cookie upgrade. Always leave one tab open with wrinklers, so if all the other tabs fail to give you a cookie upgrade, you can manually save on the tab that still has the wrinklers, and repeat the process.

Icon	Name	Price (cookies)	Description	ID #
File:SkullCookies.png	Skull cookies	444,444,444,444	Cookie production multiplier +20%. "Wanna know something spooky? You've got one of these inside your head RIGHT NOW."	134
File:GhostCookies.png	Ghost cookies		Cookie production multiplier +20%. "They're something strange, but they look pretty good!"	135
File:BatCookies.png	Bat cookies		Cookie production multiplier +20%. "The cookies this town deserves."	136
File:SlimeCookies.png	Slime cookies		Cookie production multiplier +20%. "The incredible melting cookies!"	137
File:PumpkinCookies.png	Pumpkin cookies		Cookie production multiplier +20%. "Not even pumpkin-flavored. Tastes like glazing. Yeugh."	138
File:EyeballCookies.png	Eyeball cookies		Cookie production multiplier +20%. "When you stare into the cookie, the cookie stares back at you."	139
File:SpiderCookies.png	Spider cookies		Cookie production multiplier +20%. "You found the recipe on the web. They do whatever a cookie can."	140

Achievements

To help keep track of how many Wrinklers you have popped, go in the "Stats" section, then look under "Special"

Icon	Name	Description	Number
File:Itchscratcher.png	Itchscratcher	Burst 1 wrinkler.	86
File:Itchscratcher.png	Wrinklesquisher	Burst 50 wrinklers.	87
File:Itchscratcher.png	Moistburster	Burst 200 wrinklers.	88
File:SkullCookies.png	Spooky cookies	Unlock every Halloween-themed cookie. Owning this achievement makes Halloween-themed cookies drop more frequently in future playthroughs.	89

Trivia

Owning the achievement "Spooky cookies" makes Halloween-themes cookies drop more frequently.
In the game's code, next to the code that tells the wrinklers to return 110% of their sucked cookies is the comment "cookie dough does weird things inside wrinkler digestive tracts".
The flavor text for the Ghost cookie ("They're something strange, but they look pretty good!") is a reference to and parody of the famous line in the theme song for the 1984 film Ghostbusters, "There's something strange, in the neighbourhood" and "When there's something weird, and it don't look good".
The flavor text for the Bat cookie ("The cookies this town deserves.") is a reference to a famous line from the 2008 film The Dark Knight, in which the character Lt. James Gordon states that Batman is "the hero Gotham deserves."
The flavor text for the Spider cookie ("You found the recipe on the web. They do whatever a cookie can.") is a reference to the web-slinging Marvel Comics character, Spider-Man. Aside from the spider pun in the first sentence of the flavor text, the text also parodies a line in the theme song used for various Spider-Man media, "Spider-Man, Spider-Man. Does whatever a spider can." "The web" refers to either the internet or the actual spider.
The flavor text for the Slime cookie ("'The incredible melting cookies!'") is a reference to the 1977 film The Incredible Melting Man'.
The flavor text for the Eyeball cookie ("When you stare into the cookie, the cookie stares back at you.") is a reference to a quote by the german philosopher Friedrich Nietzsche, "when you gaze long into the abyss, the abyss also gazes into you". It could also be a reference to a quote by Sister Jude, a character in the show American Horror Story: "If you look in the face of evil, evil's gonna look right back at you.
The wrinklers somewhat resemble Crimeras from Terraria, although Crimeras were implemented after wrinklers.
The "Moistburster" achievement may be a reference to "Voidthirster ", a card from Ascension . It is also reminiscent of the bloodthirsters from League of Legends and Warhammer. Or perhaps it is a more obvious reference to the Alien Franchise's Chestburster.
Prior to the v1.0453 update, Wrinklers disappeared when you closed the Cookie Clicker window or exited the browser.
The fangs of the Wrinkler somewhat resemble a left hand. (Large fang being the middle finger, fang to the right of the large fang being the pointer finger and so on).

Bugs

When a wrinkler appears, the vignette (they are yellow if in a cookie frenzy, red in clot, black otherwise) disappears until all of the wrinklers are popped/on the cookie.
Clicking on a Golden (or Red) Cookie, Reindeer, or Bunny while it is on top of a Wrinkler will also count as clicking on that Wrinkler.