Anime Deck based on the Deck Mokuba Kaiba STOLE during Duelist Kingdom. We saw a whopping 2 cards of said Deck, so the rest is up to interpretation.
Duelist Kingdom has different rules than the current ones (those would only take place in Battle City), so duelists are able to summon high level monsters for no tributes. This deck was made for fun and wasn't meant for being competitive (there were NO attempts at making this deck any good, really).
So what was the Duelist (that Mokuba stole the deck) thinking exactly? Who would use cards like "Man-Eating Plant"? Well, perphaps, they were using a Plant Deck! To make usage of Fairy King Truesdale's and Wodan's effect, I assume.
Oh seems viable enough for Duelist Kingdom Decks- but hey what's that? "Krokodilus"? So Reptile monsters too? Something tells me a "Swamp" card existed in the anime, it was just never shown.
Millenium Duels gave Mokuba a "Reptile Plant Deck", and since we didn't see the other cards in the anime, that'll do. I just tweaked it all a bit to make more sense in this era.
Couldn't Pegasus have 40 duelists that were actually good? Was the game that early on back then? We're not really sure how they obtain the cards there but I guess the really good ones are just that scarce. Or perphaps, much like just copy-pasting someone else's Deck, Mokuba just didn't know how to use it properly.
Mokuba, please, next time adjust the Deck before using it, alright? Your brother is rich and has some neat cards to help you.
The Side Deck is full of cards that Mokuba is usually seen using in the games (they're pretty neat and much better options).
"Snatch Steal" isn't a card he is usually seen using, but you can kinda see where this is going.
Was hella fun building this trash Deck.