Animated animals and pint-sized aliens. Museum relics that come to life at night. Magic rocks that make wishes come true. A bouquet of balloons big enough to lift a house into the sky. Fantasy and fun take centre stage in summer's crop of family films.

It all began last weekend with Night at the Museum: Battle of the Smithsonian. Ben Stiller reprises his role as museum security guard Larry Daley, who faces off with exhibits that come to life at night. He's joined by an all-star cast - Amy Adams, Robin Williams, Owen Wilson, Christopher Guest, Ricky Gervais, Jonah Hill, Hank Azaria and others - as he attempts to rescue a couple of relics shipped to the iconic museum by mistake.

The film boasts a bigger cast, scope and setting than the 2006 Fox original, said director Shawn Levy. "The first determination was to ... enlarge the scope of the movie visually, and shooting at the world's biggest museum definitely helped do that," he said. "But more important was deeper story and characters. So many sequels are bloated and bigger and louder, but less interesting.

This movie is very much about Ben Stiller's character and his relationships with not only the love interest in Amy Adams' Amelia Earhart, but versus the villain in Hank Azaria, so it becomes a much more dynamic movie."

The fantasy-driven fun continues this weekend with Pixar's latest offering, Up. The 3D animated film follows an old balloon salesman, voiced by Ed Asner, who takes off on the adventure of a lifetime when he uses his helium-filled wares to lift his house into the sky.

Up in the clouds, he discovers he's accidentally brought along an annoying stowaway - an overly optimistic eight-year-old kid. Director Pete Docter and co-director Bob Peterson combined two key elements to dream up the story: Their love of the house-on-balloons visual and the fun of a "grouchy old man character," Docter said.

"It's just fun to draw, fun to animate," he said. "He can get away with saying things and being kind of a curmudgeon and a jerk, that most other characters you go, 'Oh, I don't like him.' "But he's earned it. He's 78 years old. What are you going to say to him, you know? So it was those two elements kind of fusing together that brought this story."

Robert Rodriguez looked to his life - and his children - for inspiration for his latest family flick, Shorts. He and his kids came up with the idea of a magic rock that can make any wish come true while they were making "backyard movies," Rodriguez said.

Suddenly he knew this would be his next family film. "I thought, 'This is a good angle for a feature. This should go beyond our little backyard movies to show ourselves," he said. "It's just open for a lot of creativity and a lot of ideas and a lot of fun, especially as the rock passes from child to child and family to family and parent to parent ... We have almost a Little Rascals slew of kids from different families that live in this neighbourhood get their lives changed by this magic rock that shows up after a thunderstorm."

Rodriguez, whose credits include the Spy Kids films as well as more adult fare such as Sin City and From Dusk Til Dawn, said the film is perfect for all ages because "wish fulfillment is something we don't grow out of."

That's the key to a successful family film, he said: All-ages appeal and a feeling of empowerment for the youngest viewers. "Kids feel like they can do things in the world, yet they still need their mom to drive them to the mall," he said. "They can't go make moves on their own yet, so if they get to see other kids being empowered, that's a fantasy quality for them, and the wish fulfillment in this movie plays a big part of that."