John Flansburgh is one half of They Might Be Giants. There is another tumblr dedicated to the band’s other half, John Linnell, and yet another tumblr dedicated to the band itself: Fuck Yeah They Might Be Giants.
Flansburgh (a.k.a. Flansy, Flans, the one with the glasses, the angry John with all the curse words, Agent 00-Soul) is generally considered to be the more outgoing of the two Johns; he devises the setlists for shows and will occasionally sign things for fans afterward. He had a side project called Mono Puff that is occasionally featured on this tumblr as well, but the majority of his work is done with TMBG.