I know a few people may or may not have thought of this, however some of the Pokemon I picked for each Turtle suits their personalities and have stories of how they got those Pokemon.
So here we go!
*Undertow (Vaporeon, Male)- What better Pokemon to fit well with the Turtles' brotherhood than the Eevee-Lution line.
Each brothers' Eevee evolving differently, and Leo named his Eevee after it found a Water Stone in the sewers.
*Excalibur (Aegislash, Male)- To represent Leo's nobility, chivalry, and his Katanas
*Bandit (Lucario, Male)
*Cutter (Scyther, Male)
*Scout (Froakie, Male)- Well Froakie's finally form is a ninja frog so....
Leonardo belongs Mirage, Laird & Eastman, and Nickelodeon
Pokemon belong to Pioneer, Nintendo, and Game Freak