2012 plots followed up in the New Animated adventures comics.
 

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I recently discovered this series and I thought I should point this out to fellow fans of the 2012 series.

This comic book series actually fills in a lot of blanks that the series itself chose to ignore.

As such, SPOILER ALERT!

- There's a background story on Xever, how a childhood friend ratted him out to the Police and he got locked up. The fight between the Turtles and Fishface who has tracked his old buddy down, takes place on a cruise ship, which seeing as how it takes place during season one, meant that this is the first time they actually fight him in the water.
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- The military Junkyard Donatello mentions a couple of times during season one is showcased as Donnie and April try to raid it for parts for Donnie's new invention. This also is a crowning story of awesome for April.
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- There is a story in which the girl from the "Slash and destroy" episode shows up again and it is revealed that Leonardo has continued to visit her for tea.
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- In several issues we get to see just how big the Purple Dragon gang is, they are far more numerous than just Fong, Sid and Choi

- And we get more character development of our heroes in a half shell.
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Chloe
 

And it was the comics who first gave the little girl the name Chloe.

I recognise the 'chloe' strip from one of the UK TMNT magazines, not sure if these include all of those stories? not seen too many of them anyway.

Tea-Time for a Turtle
 

She debuted in Tea-Time for a Turtle, Part 1, originally published in TMNT Amazing Adventures #5, first released on 9 December 2015

http://tmntentity.blogspot.com/2015/...es-part-1.html

Did they ever do anything with Timothy aka Mutagen Man? That was one loose end that really bothered me never to have gotten wrapped up.

No, the comics didn't touch him for that reason. He was left to die.

The comics gave a lot more stories to the secondary mutants like Spiderbitez, Snakeweed, Squirrelnoids, Muckman, Napoleon Bonafrog, etc....almost all the mutants who only had 1-2 episodes in the main show got another story or two in the comics...so if you want to see more of them there you go.

How many issues did the 2012 comic have? Any big continuity errors?

Issues
 

New TMNT Adventures had 24 issues, published between July 2013 and June 2015. Amazing TMNT Adventures had 14 issues, published between August 2015 and September 2016.

http://tmntentity.blogspot.com/2011/...ublishing.html