Yes, a challenger has beaten an iron chef numerous times.
The first ever episode in Iron Chef America was in 2004 - The Battle of the Masters. The first battle was between Chef Bobby Flay and Chef Hiroyuki Sakai. The secret ingredient was "Trout". Chef Bobby Flay won the battle with a score of 55-51 in his favor. After this, Iron Chef America as a TV Series has been very successful is currently in its 11th season.
Sure, why not. Iron Chef Masaharu Morimoto is one of the original Iron Chefs and has been competing ever since the first series of Iron Chef America. He last competed in Season 11 against Chef Homaru Cantu in battle Herring which he won. As of now, he is expected to compete in the Iron Chef America, tournament of champions along with other Iron Chefs.
Nope
Yes. Chef Cat Cora was the first woman to ever attain the title of Iron Chef. She was one among the 5 chefs who were chosen as Iron Chefs when the series Iron Chef America started. She was the only woman iron chef until chef Alex Guaranaschelli won the next iron chef series in 2012.
Jose Garces has: Played himself in "Iron Chef America: The Series" in 2005. Played Himself - Iron Chef in "Iron Chef America: The Series" in 2005. Played Himself - ICA Challenger Chef in "Iron Chef America: The Series" in 2005. Played himself in "The Best Thing I Ever Ate" in 2009. Played himself in "Big Morning Buzz Live" in 2011. Played Himself - Iron Chef in "Iron Chef America Countdown" in 2012.
Yes, a challenger has beaten an iron chef numerous times.
The first ever episode in Iron Chef America was in 2004 - The Battle of the Masters. The first battle was between Chef Bobby Flay and Chef Hiroyuki Sakai. The secret ingredient was "Trout". Chef Bobby Flay won the battle with a score of 55-51 in his favor. After this, Iron Chef America as a TV Series has been very successful is currently in its 11th season.
Sure, why not. Iron Chef Masaharu Morimoto is one of the original Iron Chefs and has been competing ever since the first series of Iron Chef America. He last competed in Season 11 against Chef Homaru Cantu in battle Herring which he won. As of now, he is expected to compete in the Iron Chef America, tournament of champions along with other Iron Chefs.
Judy Joo has: Played Herself - Iron Chef UK in "Iron Chef America: The Series" in 2005. Played Herself - Judge in "The Next Iron Chef" in 2007. Played herself in "The Best Thing I Ever Ate" in 2009. Played Iron Chef in "Iron Chef UK" in 2010. Played herself in "The Best Thing I Ever Made" in 2011.
Nope
Simon Majumdar has: Played Himself - Judge in "Iron Chef America: The Series" in 2005. Played Himself - Judge and Food Writer in "Iron Chef America: The Series" in 2005. Played Himself - Judge in "The Next Iron Chef" in 2007. Played himself in "The Best Thing I Ever Ate" in 2009. Played Himself - Judge in "Extreme Chef" in 2011. Played Himself - Guest in "Iron Chef America Countdown" in 2012.
Marc Forgione has: Played Himself - Guest in "Good Morning America" in 1975. Played Himself - Chef in "Live with Regis and Kathie Lee" in 1988. Played Himself - Guest in "Live with Regis and Kathie Lee" in 1988. Played Himself - Sous Chef: Laurent Tourondel in "Iron Chef America: The Series" in 2005. Played Himself - Sous Chef: Larry Forgione in "Iron Chef America: The Series" in 2005. Played Himself - Iron Chef in "Iron Chef America: The Series" in 2005. Played Himself - Team Iron Chef America in "Iron Chef America: The Series" in 2005. Played himself in "Rachael Ray" in 2006. Played Himself - Contestant in "The Next Iron Chef" in 2007. Played Himself - Guest Judge in "The Next Iron Chef" in 2007. Played himself in "The Best Thing I Ever Ate" in 2009. Played Himself - Iron Chef in "Unique Eats" in 2010. Played himself in "Big Morning Buzz Live" in 2011. Played Himself - Iron Chef in "Iron Chef America Countdown" in 2012.
Yes. Chef Cat Cora was the first woman to ever attain the title of Iron Chef. She was one among the 5 chefs who were chosen as Iron Chefs when the series Iron Chef America started. She was the only woman iron chef until chef Alex Guaranaschelli won the next iron chef series in 2012.
As of April 2013 - No. There have been a total of 11 seasons of Iron Chef America and there has never been an episode named easy bake oven edition. There have been thanksgiving specials, Christmas specials etc but never an easy bake oven special. Maybe it will come in future, but as of now, the answer is No.
Masaharu Morimoto has: Played himself in "Live with Regis and Kathie Lee" in 1988. Played himself in "Morimoto R.A.W." in 2002. Played Iron Chef Japanese in "Iron Chef America: Battle of the Masters" in 2004. Played himself in "The Making of Iron Chef America" in 2004. Played Himself - Iron Chef in "Iron Chef America: The Series" in 2005. Played himself in "The Next Food Network Star" in 2005. Played himself in "Iron Chef America: The Series" in 2005. Played himself in "Anthony Bourdain: No Reservations" in 2005. Played Himself - Team Food Network in "Iron Chef America: The Series" in 2005. Played himself in "Bizarre Foods with Andrew Zimmern" in 2006. Played himself in "Throwdown with Bobby Flay" in 2006. Played Himself - Judge in "The Next Iron Chef" in 2007. Played Himself - Guest Judge in "The Next Iron Chef" in 2007. Played himself in "At the Table with..." in 2007. Performed in "Iron Chef America: Supreme Cuisine" in 2008. Played himself in "The Best Thing I Ever Ate" in 2009. Played Himself - Chef Morimoto in "Hawaii Five-0" in 2010. Played himself in "Big Morning Buzz Live" in 2011. Played Himself - Guest in "The Chew" in 2011. Played himself in "Restaurant: Impossible" in 2011. Played Himself - Judge in "Miss Universe 2012" in 2012. Played Himself - Iron Chef in "Iron Chef America Countdown" in 2012.
Sean Brock has: Played Himself - Guest in "The Charlie Rose Show" in 1991. Played Himself - Challenger Chef in "Iron Chef America: The Series" in 2005. Played Himself - Executive Chef, Husk in "The Best Thing I Ever Ate" in 2009. Played Himself - Chef in "Unique Sweets" in 2011. Played himself in "Mind of a Chef" in 2012. Played Himself - ICA Challenger Chef in "Iron Chef America Countdown" in 2012. Played Himself - Host in "Mind of a Chef" in 2012.