Donatello, the Brains {2}{U}
Legendary Creature — Mutant Ninja Turtle
BlueCommander: legal
Identity
Blue
EDHREC rank
#6,945
Cheapest printing
US$1.11
TCGplayer
Printings
2
If one or more tokens would be created under your control, those tokens plus a Mutagen token are created instead.
Partner—Character select (You can have two commanders if both have this ability.)
Keywords: partner
Every printing
highest TCGplayer market first; a card with only a thin single listing shows its low
In short
A Commander deck is a commander and 99 other cards, one copy of each (except basic lands), all inside the commander's colour identity. Paste a full list into the deck price calculator to price it and check it against the format.