Nickelodeon Kart Racers 3: Slime Speedway has all the aspects you expect from a Mario Kart style game. There are 3 difficulties, 10 cups with 4 races each (but there's only 36 tracks since the last cup reuses 4, many are returning from the previous game).
The graphics are bold, crisp and colourful. At first, I thought the courses seemed a bit generic as most weren't noticeably representative of the shows. But I suppose I haven't watched cartoons for 20 years, so maybe I had less chance of spotting references. In the previous game, I thought many moving obstacles across the courses look generic and move generically (so just a stock object moving back and forth). There's still elements of that, but some obstacles have a much improved look. The courses do look and play well, I just feel like some of them just needed that extra personality to be obviously Nickelodeon when you glance at a static image.
There's a large and fantastic character line-up, from: Teenage Mutant Hero Turtles, Ren & Stimpy, Rocco's Modern Life, Spongebob, Rugrats, Hey Arnold, CatDog, then some more modern ones that I have heard of like Avatar The Last Airbender, alongside unfamiliar ones to me like: Invader Zim, Danny Phantom and The Loud House. One thing they fixed from the previous game is adding voice acting so now the characters have more personality.
You choose a character, kart/bike, wheels and exhaust. The game remembers your last selection and allows you to save a few presets too which is very useful. If someone has a setup they always used, they can easily select it. I like working my way through the character and kart list so it was helpful for me. The same doesn't apply to the races though so you have to scroll through the cups or tracklist after you complete a cup/time trial etc which is really annoying.
An interesting mechanic that remains from the previous game is that you choose 3 supporting characters as pit crew. 2 are auto abilities, and 1 gives you a special ability that you can trigger when your slime gauge is full. You can imagine how some of these can work well together, so I'd imagine the community would have come up with "overpowered" combinations.
I always like unlocking things in games, so it was nice to see new racing characters, supporting cast, and car customisations (body, exhaust, paint jobs) were unlocked at different points. Some you unlock by completing the Challenge mode, gained by beating set times in Time Trial, winning in Grand prix, then the rest are purchased in the shop. There's plenty to buy so you will need to play the game a lot in order to unlock everything. 150-170 tokens are required for characters, so when it is 10 tokens max per race, you end up playing a few cups to unlock a character. I love lots of things to unlock, so I was fine with this system but others may find it a bit grindy. Helga is locked behind online mode which is dead.
Bikes have also been added, so it's not just Karts. There are water sections where your vehicle transforms into a boat which has been seen in Mario Kart and Sonic Racing.
The racing is what you expect from these games, so you are encouraged to drift to gain a boost, or leap off ramps to get a boost after a "stunt" animation. You drive through slime (or collect slime coins) to fill your special gauge. Collecting slime coins also gives you a slight speed boost just like Mario Kart. Since there's boost pads, ramps, and tight corners; it feels like you constantly boost which is maybe why it's hard to hit anyone with the weapons.
The weapons generally behave the same as the classic Mario Kart ones. There's a homing American football (red shell), toy ball (green shell), gnome (banana), and many more. The weapon use was quite high in the previous game. Maybe they tweaked it here due to criticism but maybe too much since it felt the game was mainly racing. Weapons like the toy balls didn't travel too far before disappearing so you don't experience situations like in Mario kart where you get hit by stray shells. It was rare to see hazards on the ground other than what was part of the track design. In Mario Kart you have bananas on the floor, shells bouncing around, maybe even some more annoying items like the blue shell and chain chomps that can come charging from behind.
Another reason why weapon use seems low is that the tracks contain a fair few branching paths like shortcuts and the specific "slime speedway" which is a fast on-rails section where you only need to jump over the barriers.
Some of the alternate routes often seem easier to spot/get on than the main route, but then not all alternate routes are equivalent or quicker. It’s worth testing out each track in time trial to find the optimal routes.
I did enjoy the previous game and could see elements where they could improve. With some tweaked courses, larger character roster and the inclusion of voice acting; it should have been amazing. However, the weapon mechanic isn't as good so still not quite right. Nickelodeon has such a good range of characters and content, their games could easily be up there with Mario Kart if they really backed them.