When Liz is in Jack's office and she works out that Dennis is the Rat King, Liz can be seen wearing a wedding ring.
Late in Dennis's line "Eventually, their bodies fuse together and they form a multi-headed, live rat king, and we saw one," the camera cuts to him not talking.
Dennis states that New York City has 17 rats for every human resident. Actually, people in NYC outnumber rats by about 4:1.