On first watch, "Battle of the Humungonauts" was a good if not great episode. With lots of good things, but also with a few aspects that could have been done better. 'Scooby Doo: Mystery Incorporated' to me has always been one of the better Scooby Doo shows and the show was showing enormous promise prior to this and with this with all the previous episodes ranging between good and close to great. Not just on first watch, but also on subsequent rewatches.
"Battle of the Humungonauts" continues this very high standard that was obvious in the previous episodes and is still the good if not quite great episode that it was on first watch. Which is good enough for me actually, do not like it when something goes significantly down in my estimations on rewatch, a distinction that the show never got near luckily. The good things are many, and the best are more than great. There are also a few things that could have been done better, but actually little really is executed disastrously apart from one aspect that did nothing for me and could easily have been left out with no issues.
The animation is beautifully detailed, vibrant and full of atmosphere. Absolutely loved the spooky animation for the abandoned harbour. The music is still dynamic and has the right amount of spookiness and mystery without over-emphasising. The theme music is still catchy. The character writing is mostly great, with the biggest joy being Stone in the relationship counsellor role which was very funny and cued some priceless lines from Stone. Enough of the atmosphere in the mystery is creepy and the sinister looking villains are a further advantage.
Also really liked Mr E's radio trick, which really intrugued, and although the denouement is mostly very predictable it does throw in a very unexpected surprise concerning the responsible. The voice acting is great, Matthew Lillard is spot on as Shaggy and Patrick Warburton is deadpan perfection as Stone.
Was really not taken however with the rather cheesy and soapy Shaggy and Velma subplot and felt that it distracted from the mystery and took over too much.
The mystery is diverting enough and atmospheric, but on the slight side (the atmosphere and the character moments save it) and is further let down by the truth being far too obvious too early.
In conclusion, good but not great. 7/10.