Popbob was an infamous troll, and Griefer who joined in early 2011 from 4chan, and is now inactive. She is significantly famous among 2b2t and other servers due to being popularized and subject in many videos by youtuber FitMC. As of today, she is used in various memes relating to 2b2t. Popbob is notorious for supposedly having griefed more bases than any other known player on the server, although this achievement has been long been contested by jared2013.

More facts here: https://2b2t.miraheze.org/wiki/Popbob