ARGENTINA
How qualified: CONMEBOL 4th place
Population: 40.9 million
Capital: Buenos Aires
Team nickname: La Albiceleste ("White and light blue")
Best World Cup finish: 1st (1978, 1986)
Coach: Diego Maradona (ARG)
Guys to watch: Lionel Messi, Javier Mascherano, Carlos Tevez
Why cheer for them: Messi, maybe the best player in the world.  And he still looks like a kid.
Why boo them: Maradona, for so many reasons.

NIGERIA
How qualified: CAF Group B winner
Population: 149 million
Capital: Abuja
Team nickname: Super Eagles
Best World Cup finish: Second round (1994 and 1998)
Coach: Lars Lagerback (SWE)
Guys to watch: Obafemi Martins, John Obi Mikel, Yakubu Aiyegbeni
Why cheer for them: An exciting team full of terrific athletes.
Why boo them: They've been overrated and under-delivering for years now.

SOUTH KOREA
How qualified: AFC Group B winner
Population: 48.5 million
Capital: Seoul
Team nickname: Taeguk Warriors (Taeguk relates to levels of martial arts as well as the symbols on the South Korean flag)
Best World Cup finish: 4th place (2002)
Coach: Huh Jung-moo (KOR)
Guys to watch: Park Ji-sung, Park Chu-young, Lee Chung-yong
Why cheer for them: As hardworking a team as you'll see in the tournament.
Why boo them: For your broken-down Hyundai.

GREECE
How qualified: Beat Ukraine in playoff
Population: 10.7 million
Capital: Athens
Team nickname: Often referred to as To Piratiko ("The Pirate Ship") or Galanoleyki ("Blue and White")
Best World Cup finish: First round (1994)
Coach: Otto Rehhagel (GER)
Guys to watch: Giorgos Karagounis, Theofanis Gekas, Angelos Charisteas
Why cheer for them: Australia's strong Greek heritage. And coach "King" Otto Rehhagel is a bit of a character.
Why boo them: Can often display the worst of European football: diving, complaining, quitting.