Scooby-Doo! Mystery Incorporated - 2010-2013
I would recommend this show for age 12+ because of the last couple episodes. They are genuinely terrifying.
This show can definitely cause nightmares. The animation is great; but, the plot lines are incredibly scary.
The show touches on subjects like sexism, fate, panic attacks, ghosts, parental defiance, and love. It has many anti-lessons.
Adventure Time - 2010-2018
Finn and Jake are constantly killing living beings. Sometimes the fights can be pretty gorey. It can definitely cause nightmares.
This show can be genuinely terrifying. The animation is either really cute or really scary. It can be hard to watch. I would only recommend this for kids 15+.
There are a lot of anti-lessons as well. Example: you shouldn't help jerks. Finn's robot arm is also very unrealistic as a usable prosthetic.
Gravity Falls- 2013-2016
If your kid has a difficult time differentiating reality and fantasy, this show is not for them. It could cause nightmares. The last episode is horrifying.
I wouldn't let children under 12 watch this show. It features paranormal activity a lot. It also talks about death and the concept of ghosts/haunting.
This show also talks about there being multiple dimensions. The kids' great uncle gets lost in another dimension and is saved.
Steven Universe - 2013-2019
There are some anti-lessons. Example: children are entitled to know everything about their parents' lives.
I would recommend this show to children that already understand intimacy, death, and war. These are the main topics of the show.
This show often touches on subjects like racism. There is also a scene that says the government corrupts. These topics may be too mature for young children.
Star Vs the Forces of Evil - 2015-2019
There are some anti-lessons. Examples: children deserve the freedom to go wherever they please; it can be good to lie to your parents.
This show is good for kids who already know right from wrong. Star can be very selfish and destructive.
There is also mention of war, colonization, and racism. The monsters in Mewni are treated as minorites,