Stephen Amell as Casey Jones, left, and Megan Fox as April O'Neil star in the science fiction action comedy “Teenage Mutant Ninja Turtles: Out of the Shadows.”

“Teenage Mutant Ninja Turtles: Out of the Shadows” is a Saturday morning cartoon on Michael Bay steroids. For the under 12 set, that's fine. For the rest of us? It's something to actively avoid.

This “Teenage Mutant Ninja Turtles” sequel, produced again by Michael Bay and directed by Dave Green (“Earth to Echo”), is so inane that they essentially have to resurrect the main conflict from the first, when the four pizza-crazed reptiles took down Shredder, New York City's resident bully. “Out of the Shadows” kicks off with Shredder (played this time by Brian Tee instead of Tohoru Masamune) breaking out of a police convoy, and effectively escaping the Turtles' nunchuck-wielding, manhole cover launching garbage truck/war machine.

The objectives of the bad guys are a little grander this time. Shredder teams up with the mad scientist Baxter Stockman (Tyler Perry, chewing the scenery somewhat gloriously) to try to open up a portal to another dimension so that Krang — a truly grotesque disembodied alien brain that one of the Turtles refers to as “chewed gum with a face” — can take over Earth. I think. It involves portals and black holes and a purple ooze that can change humans into animals. Baxter explains that all humans have a latent, essential animal in their genes. With a swift dart to the neck, he transforms the thugs Bebop (Gary Anthony Williams) and Rocksteady (WWE star Stephen “Sheamus” Farrelly) into a warthog and rhino.

The plot, of course, is over-the-top gobbledygook. A conflict-of-the-week done on a massive, hundred million dollar scale, that pauses from the set-pieces once in a while to leer at Megan Fox. Her April O'Neil is, in her first five minutes on screen, made to wear a tiny schoolgirl outfit that she changes into mid-stride in a public place.

Fox, once again, is Teflon here. She fares fine, and better than most of the humans, including Will Arnett, who is back as the cameraman turned New York City hero Vernon Fenwick. His slime ball celebrity shtick feels like a skipping record. Stephen Amell joins as Casey Jones, an earnest dolt who's pretty handy with a hockey puck, but who needs a little work on his one-liners.

And then there's Laura Linney — three-time Oscar nominee and general class act Laura Linney — playing the skeptical police chief for some ungodly reason.

You need look no further than the fluttery vocal stylings of Brad Garrett's Krang to really know that this is just a more expensive, high-definition version of the thing you used to watch in your pajamas while eating a bowl of cereal. If that sounds like a good thing, “Out of the Shadows” might be for you. But for most of us, the joys that the Teenage Mutant Ninja Turtles were able to provide had a definite expiration date, and no amount of CGI-spectacle or professional athlete or supermodel cameos are going to change that.

The “Turtles” are and always have been for the kids. They can have it.