Tsundere is a trope as old as manga itself, representation of a character acting cold by denying his/her affection for another character, for various reasons. That TvTropes article explains it better than I do.
The tsundere character is a meme, though not really related to Internet in any way. On the other hand, the catchphrase “I-It’s not like I like you or anything you d-d-dummy!” is very widespread on Internet, and the way of writing posts by making it as you were kind of stuttering, with a note of shyness, is commonplace on some boards.
I’m sure some of you remember about those /b/ threads featuring a drawn character from Touhou writing “I-I-I like you a-anon” or the like, which was considered kind of forced at the time. This is, of course, appreciated by weeaboos.
it’s also commonplace to have the “You have 10 seconds to be as tsunder as possible” game.
Thoughts about it?