As expected, the outcome of this investigation is nada, nothing, zilch, a big fat zero. To be honest, I can't recall an episode in which quality evidence ever surfaced. A couple of "hmm" moments, to be sure, but I'm talking about the meat-and-potatoes "wow" moments. I think those must come from extensive and persistent efforts in the field and not a maybe-we'll-get-lucky-but-if-not-we've-got-some-cheap-CGI-filler-and-a-voice-over philosophy. So, no giant rats.
However, when I was a kid, I went to an old three-story brick school that had a basement with a secret passage. I slipped inside once, discovering it opened onto what was once a large cavernous space, perhaps an earlier boiler room. There, in its dark recesses, I saw a rat that - to my young, eager eyes - seemed to be the size of a cat. I, of course, wasn't much larger than one myself. So, maybe perception has everything to do with how big a Burmese python appears (especially when you're not used to seeing them in the yard) or how a local Sasquatch might be viewed as a "werewolf" to a community of German descendants raised on such fables. And just perhaps a rat can seem really big to those for whom it serves as proxy in the fish-that-got-away tales of the concrete wilds of New York City.