The Muppets were formally inventive long before Charlie Kaufman came on the scene. Their big-screen debut opens with a raucous premiere screening of … itself, wherein the Muppets gather to watch the picture they’re in. When Kermit – a usually bright and cheery presence – slips a sarcastic remark under his breath, he often does so while looking right into the camera. Despite that sort of sophisticated self-reflection, the true appeal of The Muppet Movie is far simpler. As films get more and more technologically advanced, hand-made, lo-fi children’s pictures such as this only increase in charm. Creator Jim Henson and his puppeteers got a much bigger budget here than they had for their television show, but it seems to have mainly gone into more felt.