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Movies like Blarney - It Ain't No Picnic (1994)

Blarney the Dinosaur, Barney's evil twin brother, gets turned down for a Stephen Spielberg movie (it is assumed to be Jurassic Park, which came out a year earlier) in place of his kinder brother. He then joins the "Backdoor Gang" for a barbecue. The "kids" (played by adults) sing songs with Blarney and have fun at their barbecue. In the end, it turns out to be a nightmare that Blarney had.