Once Walter obtains a card that grants his wishes the "shooting star" card. The astronaut goes into a panic and looks for Danny in the boys room. When he can't find Danny he starts to snap at Walter. Only for Danny to come out from under his bed and demand that the man leave Walter alone. This is heartwarming because moments before Danny hid under his bed because the two boys had just been fighting (again).
Walter: The card worked...
Astronaut: Yeah it worked, congratulations were stuck in space now forever!
Danny: Leave him alone.
Just before Walter lowers Danny down in the dumbwaiter to the basement so Danny can sneak past the Zorgons and retrieve the game.
Walter: Nothings gonna happen to yeh, okay?
Walter: Cause I'm your brother, and that's what being a brother means. I may not let anything ever happen to you.
"I wish the astronaut had his brother back."
It happens so fast that many wont catch it. But just as the Zathura black hole starts eating up the house, Lisa is the first sucked up. She's the first simply because she grabbed Walter and put herself in harms way making certain he didn't get sucked in.