Are the chosen anime within Welcome To The N.H.K. of any significance?
It always reminded me of Di Gi Charat ("Dejiko") but I don't have any evidence that this was intentional. Visually they're pretty similar, and both are sort of used as mascots (Di Gi Charat being the mascot for the Broccoli gaming company). They also both append random words to the end of their sentences (e.g. "purin"). Additionally, according to Wikipedia:


  An animated Dejiko and her sidekick Gema first appeared on in a television advertisement for Gamers, set to the store's theme song, Welcome! by Hiroko Kato




But again, don't know any official source that says one way or another about the similarity.