The 12 feeder puzzles, in the given order, each contain one of the 12 Labours of Hercules:

#	Puzzle	Answer	Hidden labour
1	Frogtongue	IFIHADAMILLIONDOLLARS	LION
2	Cookies	CARBOHYDRATE	HYDRA
3	Introspection	HINDRANCE	HIND
4	Extreme Tapeover	SCHEDULEBOARD	BOAR
5	Counterparts	CONSTABLE	STABLE
6	Getaway Car	BLACKBIRD	BIRD
7	Excitement, and factorial!	EBULLIENCE	BULL
8	Hidden Delicacies	AMARELLE	MARE
9	Cycles	BELTWAY	BELT
10	Hotkeys	SCOWL	COW
11	Captchas	GRAPPLED	APPLE
12	Pair Coding	ENDOGENOUS	DOG

Each answer can fit uniquely into one of the sets of blanks, with the labour taking up the one box with 💪:

I

F

I

H

A

D

A

M

I

L

LION

D

O

L

L

A

R

S

E

BULL

I

E

N

C

E

B

L

A

C

K

BIRD

G

R

APPLE

D

C

A

R

B

O

HYDRA

T

E

HIND

R

A

N

C

E

BELT

W

A

Y

C

O

N

STABLE

S

C

H

E

D

U

L

E

BOAR

D

S

COW

L

A

MARE

L

L

E

E

N

DOG

E

N

O

U

S

Reading the gray cells yields the answer LIL GREY CELLS.