"Be one with nature."
As cliché as it sounds there is some merit to the idea of perfectly blending into the surroundings of a natural environment so as not to disturb the flow of its flora and fauna.
But... to become exactly like one of them? Apparently this is one of the best ideas that a Pokémon naturalist can do. Just ask our guest for today, mister Nicholai, the self-proclaimed "knickerbocker".
"Hey ya, Zigzagoon, I may have already surprised you, but I still think beating you up with my Mudkip will do the trick."
Given a cursory look, Nicholai doesn't seem like anything or anyone special in the show. In fact, he looks kind of generic, and you might even mistake him for Ash if you are only to compare their heads and let him wear the same cap. He is first encountered by Ash and his Hoenn buddies while making their way through a forest. This is after a friendly match with some rando trainer, who got beat up with Ash's Pikachu.
"You didn't think this giant Ziggy could actually be a human did you?"
At first, Max was surprised that a Zigzagoon could be so big, stating the typical size and weight of the real, average Zigzagoon. Then, the ZIgzagoon is revealed to be a kigurumi (surprise!), with Nicholai quickly taking off the kigurumi to land the final Pokéball and catch his target.
"Zigzagoon, wait! I technically 'encountered' you already a moment ago!"
"Well gee, thanks for distracting(?) me back there!"
... Which failed, by the way. Unfortunately things didn't go his way, with the two siblings disrupting him long enough to be unable to catch up the escaping Zigzagoons.
"I am Nicholai, the knickerbocker! I'm using the term incorrectly you say? This is the Pokémon world you dummy!"
While he introduces himself as an expert Pokémon naturalist, he also expresses his pure love for knickers. In fact, he quickly forgets his annoyance with the two, and immediately reconciles with them as soon as he notices the shorts they are wearing.
"Yeah, you guys can go on your way. Not interested in non-knickerbockers y'know."
"But, we're the ones who can actually roll our trousers up for that."
As for Ash and Brock, well he never paid much attention to them initially,and these trouser wowzers actually going to sit on the sidelines for most of Nicholai's special episode.
"Oh that's easy. Just cry out the name of the Pokémon as you're mimicking them."
The motto of being one and communicating your heart with the Pokémon is very strong for Nicholai. In fact, it probably is the main message(?) of the episode he initially featured in. This was also additionally conveyed with Pikachu's consistent coordination with Ash, and the apparent inability of May to do the same for her Torchic.
Speaking of Torchic, Nicholai also showcased a good number of other Pokémon kigurumi throughout his 20-minute showtime limit. Enumerated, these are:
Zigzagoon kigurumi. It is the most that we get to see out of this episode, 'nuff said.
Mudkip kigurumi. Pretty straighforward, nothing fancy, and it probably helps him sync with his Mudkip better. Potentially also an aquatic suit of some kind (unconfirmed). You wouldn't want to touch grasses using that suit though.
Aipom kigurumi. Primarily used to significantly boost his running speed while going after Team Rocket. Which is weird, since monkeys aren't exactly known for their sprinting speed. He could have just used some other Pokémon kigurumi for that (especially since he went all-fours anyway while running).
Gligar kigurumi. The Pokémon kigurumi that Nicholai used to rescue his Mudkip from Team Rocket. Certainly has more compatibility for its use, especially considering its type compared to its affinity with the other Pokémon kigurumi that he had showcased so far.
Tentacruel kigurumi. It wasn't featured specifically on anything, just showcased during his introduction. Possibly having aquatic features as well.
Bellossom kigurumi. Also only briefly showcased during his introduction, so no other details were revealed or explained.
"If I beat her here, then I've essentially beaten his dad, the Petalburg City Gym Leader!"
"Umm, I'm essentially an entirely different person than my dad."
As shown by the series, Nicholai can be quite impulsive when it comes to his frustrations. But this exact method of quickly springing to action is what saved him, his Pokémon, and Ash's gang several times. So, it wasn't really that bad of a trait.
"Good thing I didn't choose a flying Pokémon kigurumi that I'd flap my arms with."
Plus, he's probably one of the few guests in the show that managed to solve his issue with Team Rocket pretty much immediately. Like, he was able to successfully retrieve his Mudkip just mere minutes after Team Rocket took it away from him. Not even our almighty Tyrantrum was able to do that with such swiftness.
"Yup, my dad was able to beat up Ash good that time."
"So if the Petalburg Gym Leader is that strong, then I guess it's not easy after all."
At the end of the episode, Nicholai managed to settle his issues with the discouraged May, and even got to be buddies with her brother Max. As for Ash, he was once again challenged to an obligatory Pokémon battle, which of course, he won. Upon learning that even Ash could not beat May and Max's dad, the Petalburg Gym Leader (at that point in time), Nicholai then conceded his idea that it would be a piece of cake.
And that is our introduction to Pokémon Kigurumi Extraordinaire, Nicholai. A pretty worthy rival to another kigurumi lover, we'd say. He manages to even combine form and function to his kigurumi escapades.
... so it's very unlikely that this is the last time we are going to see him in Pokémon the Series: Ruby and Sapphire.