One of my friends saw this on the shelf with my other Muppet movies and asked how it was. I told her, "Well, a Muppet purist wouldn't own it, but a Muppet completist would." So she said that made plain which type I was.
It isn't Muppet "canon"--that is, it won't fit into the "true" Muppet storyline established in, say, the Muppet Show and The Muppet Movie. This Kermit backstory is incompatible with the established chronology. I say it's apocryphal and does not take place in the "Muppet-verse."
It's also extremely lame. The jokes are weak, the plot is ho-hum, and the human actors should never, ever have been allowed into a Muppet production. Some people can work well with Muppets, some can't. These can't, and it doesn't help that they're given such cardboard stereotype characters to play. "Hi, I'm the relentless, irritable, villainesque scientist-type!" "Hi, I'm his dopey, bumbling assistant!" Sheesh.
The best part of the DVD is what's in the extras. I laughed much more at those than at the actual movie. I wouldn't buy it again just for the extras--except, yes, I would buy the DVD again, because I'm a completist and want EVERY Muppet production on my shelf.