Like "Wrestle Maniacs", "Diamonds are a Ghoul's Best Friend" was an episode of 'What's New Scooby Doo' that didn't do much for me on first watch. My memories of it being great location, decent villain but weak story and that it felt bland. When rewatching the show recently, this was the one episode where memories were pretty vague other than that it revolved around ice hockey. Am not a fan of sports, but the franchise has done many sports-themed episodes and mostly very well.
"Diamonds are a Ghoul's Best Friend" is not one of the sports-themed episodes done particularly well. It is better than 'The Scooby Doo Show's' "The Warlock of Wimbledon", but of the sports-themed 'What's New Scooby Doo' it is by far the weakest. "Diamonds are a Ghoul's Best Friend" is not a terrible episode and has its moments, but like "Wrestle Maniacs" its main problem is that it is bland in too many areas and that is why first watch memories were as vague as they were.
Every episode has a particularly good asset. "Diamonds are a Ghoul's Best Friend's" is the setting, which has a wintry beauty and also a suitably chilly atmosphere. Am not a fan of ice hockey, but can see the appeal. Would have liked to have been more of it, but the hockey action is slickly animated and dynamically choreographed.
The villain is a decent one if not one of the shows most memorable. Its design is cool and shows a lot of potential and it has the creepiness right. The animation is typically very good, loved the variety of colours and textures and the action is slick looking. The music is atmospheric and groovy. The voice acting is without complaint.
It's a shame however that the mystery is very thin and atmosphere wise, other than the setting, it is also rather bland. The creepiness is missing. The pace is quite dull, making for some over-stretching. When it comes to surprises, there is practically none in "Diamonds are a Ghoul's Best Friend", too much of it has been before with much more impact and the ending was both rushed and obvious.
Other episodes succeed better in the humour, it amuses here but there is little hilarious or new and there isn't enough. Really hated how idiotically Fred is written here too. There are more memorable chase scenes and songs, both here forgettable.
In short, one of my least favourites of the show. 5/10.