The middle one I could find somebody mention online before the episode came out, the other two don't show up at all. So the middle one I think is from the LN, the other two might be anime original (or maybe just not funny enough to post online). I have a feeling these are just referencing LNs this time. The cover arts feel inspired as well.
I'm just now realising that Nukumizu's name has mizu (water) in it, and looking up the nuku part can mean "to extract" ... and they guy's hobby is water