How 03 Donatello is "sensible":
Snarks at his captors
Take off the Professor's head you know he panicked
Didn't hesitate to throw a missile at another vehicle
Throws sarcasm comments at a almost brain dead scientist
Make devices to literally 10x more deadlier than anything Foot Clan and others can come up with
Will literally kill a being to get close to his brothers
Kills Shredder
Chases Raphael with a sledge hammer
Tbf, he's the "sensible" turtle when compared to
Almost gets hoodwinked into joining the Big Bad, ends up beaten to within an inch of his life by said Big Bad and his forces while out alone, gets thrown off a bridge by an interdimensional challenger, gets ambushed and later poisoned by said challenger in the Battle Nexus, almost gets his brothers killed, repeatedly, by wading into a gang war in the city because he felt responsible for it, forgets he's a ninja and steps on a landmine, breaks under the pressure of responsibility and violently lashes out at everyone and everything Leonardo
Chooses to hide in the bad guys' van, immediately reveals his face to a potentially dangerous vigilante, almost brains his own brother with a metal pipe, has to be repeatedly held back from charging headfirst into trouble/danger because someone ticked him off, goes out alone and winds up temporarily blind in the middle of mob territory, gets chased by anti-alien fanatics when he tries to take a shortcut home Raphael.
And randomly presses buttons he has no idea what they do, gets into trouble because he's followed his stomach yet again, winds up in a car chase on Christmas Eve, blows up an evil alternate version of their father, causes chaos by deliberately detonating an enemy's hand grenades - whilst still attached to said enemy! -, flies a spaceship so badly his brothers use him as a threat to get their captive to comply, openly brags every chance he gets about being the Battle Nexus Champion Michelangelo.












