Solution: The Thing

Written by Kevin Wald

The words below the grid can be divided into 25 sets, each of which consists of three members of a four-member group. The groups, along with the missing fourth members, are:

JONES, NESMITH, TORK -> DOLENZ (last names of the Monkees)
CLUB, DIAMOND, HEART -> SPADE (card suits)
BASSES, TENORS, SOPRANOS -> ALTOS (choral sections)
FIRST, THIRD, HOME -> SECOND (baseball bases)
LEVI STUBBS JR, RENALDO BENSON, ABDUL FAKIR -> LAWRENCE PAYTON (the Four Tops)
MUNSTER, LEINSTER, ULSTER -> CONNAUGHT (provinces of Ireland)
SUE, RUDY, KELLY -> RICH (the "alliance"/"final four" on _Survivor_)
MATTHEW, LUKE, JOHN -> MARK (Gospels)
PARSLEY, ROSEMARY, THYME -> SAGE (refrain of Scarborough Fair)
MCCARTNEY, STARR, HARRISON -> LENNON (last names of the Beatles)
B AND O, PENNSYLVANIA, SHORT LINE -> READING (Monopoly railroads)
EDGE, BONO, ADAM -> LARRY (first names of U-2 members)
MALLORY, JENNIFER, ANDREW -> ALEX (kids on Family Ties)
WAR, PESTILENCE, DEATH -> FAMINE (Horsemen of the Apocalypse)
ADENINE, THYMINE, CYTOSINE -> GUANINE (DNA bases)
LIQUID, GAS, PLASMA -> SOLID (states of matter)
COMPRESSION, POWER, EXHAUST -> INTAKE (strokes of a 4-stroke engine)
BOREAS, EURUS, NOTUS -> ZEPHYRUS (the four winds)
JIANG QING, WANG HONGWEN, ZHANG CHUNQIAO -> YAO WENYUAN (the Gang of Four)
MEENY, MINEY, MO -> EENY (the universal decision method)
DECAY, SUSTAIN, RELEASE -> ATTACK (ADSR envelope characteristics)
HEART, HEAD, HANDS -> HEALTH (the four H's of 4-H)
PLOP, FIZZ, FIZZ -> PLOP (the universal relief technique)
CHOLERIC, MELANCHOLIC, PHLEGMATIC -> SANGUINE (humors/personality types)
JACK, KING, ACE -> QUEEN (honors)

To fit the extra words into the grid, the missing quarter of it must be filled in. When this is done, it looks like this:

   L K I H T F Z M W P U Y L T Z G
   D W H Q P U A I V D B A Z M M E
   A R R C I K E M P X L O R G I S
   Q T V A M N G N R Z D W A T I R
   L E L S E J N E I P H E E H N T
   S R Z B O F P Y N N Y N F Y O Q
   E L W R I G X H S I A Y M Y H U
   I J D W E N A E O N M U O N E E
   D G K O X A U M L T S A G E A E 
   R M E M D Y D I I A U N F E L N 
   L O I Z L S Z I D K R A M K T I 
   F Z R T S E Q A N E Y R I C H U 
   H L D C O N N A U G H T Y A P G
   M B L A W R E N C E P A Y T O N 
   H F F J X E D N O C E S O T L A 
   E A K I I D O L E N Z E D A P S 

The letters in the positions marked with asterisks are SEINFELDKRAMERCOSTANZA -- that is: SEINFELD, KRAMER, and COSTANZA, the last names of three of the gang on SEINFELD. The missing element is therefore BENES, Elaine's last name. (And the picture linked to by the title is appropriate, because the Fantastic Four consists of three men and an invisible woman.)