Rainbow Dash: Veemon. Veemon’s partner in Adventure 02, Davis/Daisuke, was very similar to Rainbow, enthusiastic and brash to the point of recklessness. Veemon’s shared a similar enthusiasm, but was a bit more of a wise-cracker, often finding a way to make a joke about the situation.
Rarity: Palmon. Palmon’s partner Mimi was a lot like Rarity in that she could be fairly shallow and materialistic at times while still ultimately wanting the best for everyone in the end. Palmon, despite her outwardly cheerful personality, will often reel her partner in from her flights of fancy, and is generally rather grounded. (Get it? ‘Cause she’s a plant?)
Applejack: Gomamon. In Digimon Adventure, Gomamon’s partner was Joe/Jou, bearer of the Crest of Reliability/Honesty. Gomamon’s rather silly personality contrasts quite well with Applejack’s, her being the arguably the most serious of the Mane 6, similar to Joe in Adventure.
Twilight Sparkle: Tentomon. Tentomon was the partner to Koushirou “Izzy” Izumi in Digimon Adventure, bearer of the Crest of Knowledge. Like Twilight, Izzy could get rather carried away in his desire to learn, and would often display a surprising lack common sense. Fortunately, Tentomon has more than enough for the both of them and is more than willing to reel in his partner from becoming too obsessed for their own good.
Pinkie Pie: Hawkmon. In Adventure 02, Hawkmon was partner to Yolei/Miyako, who was extremely cheerful, full of energy, and very curious about the Digital World. Her partner Hawkmon, by contrast, has a reserved and gentlemanly demeanor, even having a posh British accent in the English dub.