Costanza.jpg is a reaction image based on a still image of the Seinfeld character George Costanza (played by actor Jason Alexander) holding a baseball bat with a look of contempt on his face. On 4chan, the image is typically used to express disapproval towards greentext implication posts that would be considered out of social norms. It has also become closely associated with the phrase "I Seriously Hope You Guys Don’t Do This" (ISHYGDDT).
Origin: The still shot of George Constanza was taken from the 143rd episode of the American TV sitcom Seinfeld titled “The Abstinence,” which originally aired on November 21st, 1996. While encountering some New York Yankees players at a batting cage, Costanza strikes up a conversation with Bernie Williams and Derek Jeter, who boasts about winning the world series with his team. Constanza responds to Jeter with a smug smile while preparing to swing his bat, coyly replying “Yeah… in six games.”
According to Encyclopedia Dramatica, the image was first used on 4chan’s /sp/ (sports) board in combination with “>putting ketchup in the fridge,” a greentext phrase used to imply that an activity or choice is abnormal, sometime in early 2011.
In March 2011, a 4chan user posted an explanation of the reaction image noting that it can be used to criticize people for doing something abnormal or ridiculous, like using sandpaper in place of toilet paper.
In early 2011, Costanza.jpg appeared multiple times on /sp/ and also on /co/ (cartoons), where a blank template image of Alexander’s face spawned a series of fsjal-like derivative images. By May 2011, 4chan users began using the phrase “I seriously hope you guys don’t do this” (ISHYGDDT) in response to lines of greentext that the poster deemed ridiculous. One of the earliest archived uses of this initialism appeared on the /v/ (video games) board in response to an Infinity Ward developer who didn't use secure tripcodes to protect his account during an AMA thread.
In June 2011, the first Facebook fan page pairing the phrase ISHYGDDT with the Constanza image was created, but only gained 624 likes as of September 2012. The following month, a second Facebook fan page using both the phrase and Constanza was created, gaining more than 22,000 likes in a little over a year. The same day, a fan page specifically for Constanza.jpg was established, but it has only acquired 1020 likes.
>2011 >Not following this account #ISHYGDDT— costanza.jpg (@ISHYGDDT) July 29, 2011
On July 31st, 2011, the first Urban Dictionary definition for “ISHYGGDT” was submitted, linking the phrase to Costanza.jpg. The acronym has also been defined on the 4chan BBS and Wikitionary. As of September 2012, “ISHYGGDT” is actively used as a tag on Buzzfeed, Tumblr and Twitter, and the reaction image/phrase pairing has appeared on other message boards including MMO Champion, GameFAQs and BodyBuilding.com.
 Chanarchive – /sp/ here … do you put your ketchup in the fridge?