Alright, let’s examine the physical state of old Mikey for a second:
- Baggy, sunken eyes
- Long greasy unkempt hair that seems to have greyed prematurely (compare Mike’s hair color to the more forest-green shade of Raphael’s beard)
- Emaciated
- Multiple missing teeth
Now, aside from sleep deprivation, the usual reasons for sunken eyes are:
- Dehydration - Sun exposure - Dramatic weight loss - Aging
The first three certainly seem to be factors, but as for the last one Brandon says that 50 years is like 20 years in mutant turtle time. That means Mikey is more 30 than he is 60, but he looks way older than his given age, especially when compared to Raph.
On the subject of aging, let’s talk about that premature greying. Contrary to popular belief, grey hair isn’t connected to stress. It can, however, be connected to a vitamin B12 deficiency, which has a variety of other symptoms as well, including mental problems (such as brain fog and dementia) and chronic pain (which may explain why he’s taken to carrying a cane with him wherever he goes rather than just his nunchucks, and has a tendency to hunch his shoulders when standing idle)
But a vitamin deficiency comes as no surprise, seeing as Mikey chooses to eat the black rotten leftover pizzas in the diner rather than go out and try to forage for something that wouldn’t give the average person eight different types of food poisoning. Oddly enough, he has a means of leaving the desert and finding something else to eat. But he instead chooses to remain close to a rundown building in the middle of nowhere that… according to him… regularly leaves him exposed to acid rain and sand storms.
It’s implied that the reason Mikey never made it to Oasis is because he lost the map he made, but I don’t think that’s the case. He rode Chompy and lead his family through the most treacherous part of the journey without so much as glancing at Mira’s arm-map, and he seemed to continuously have a good understanding of where he was and where he was going like he’d taken that path a thousand times.
He knows Oasis. He could’ve gone to paradise any time he wanted, but he chose to stay in the wasteland. Not only that, but he shows serious signs of self-neglect. Lack of decent food aside, he clearly doesn’t take any care of himself, hence the sloppy unkempt appearance and missing teeth.
So, what do we know?
- He was separated from his brothers around 50 years ago, and has been unsure if they were alive since then. Leonardo, for one, is someone he’s certain is long dead
- He took it upon himself to adopt and take care of the family pets
- He ended up discovering Oasis. Rather than stay put however, he made a map and ventured out to other colonies, and was soon hailed a beloved mystic
- Eventually, something happened that caused him to run out of steam, but rather than venture to Oasis he wandered into the desert, and eventually fell into a spiral of self-neglect
