Board Thread:Ninjago Wiki News/@comment-25095204-20140703085642/@comment-30499831-20180507045218

AstraStars wrote: Warptoad wrote: They're close to 20, but can never be 20 or over it. Old/late teens, that's it, no more. https://www.youtube.com/watch?v=WxTS-I-0T3s ..that's a fan-made theory video. Creators have said they're teenagers, and that's it. They've specifically said they'll never be over 20. How about an actual official source:

https://twitter.com/TommyAndreasen/status/778145389862088704

Question: The ninja are most likely going to be ambiguously aged teens until the end of series, right?

'Tommy Andreasen, producer: I believe so. We want to keep them young and relatable.'

https://youtu.be/2kMWaHNh9Gw?t=13m35s

Dan Hageman, one of the writers: I wouldn't say 20, I would keep them all under 20.

Kevin Hageman, one of the writers: I don't think they'll ever hit their 20s.

https://twitter.com/brothershageman/status/909594849862492160

'HagemanBros Twitter: old enough. We never get into specifics because they should be eternal teenagers. The show wouldn't work so well if they had dad bods.'

A lot of fans prefer to ignore that because they think it's dumb. They're eternally teenagers, forever under 20.