In The First Encounter, The crates made their first appearance as a secret, but only as a crate car and a crate pyramid, while in The Second Encounter they took flight to follow Sam to Sirius. When Sam's spaceship gained speed and they couldn't catch up, they decided to use "hypercrate" to speed up the crate bus, but when they were about to collide with Sam's spaceship the brake to the crate bus had broke, thus it crashed on impact into Sam's spaceship.
A crate bus has a total of 24 seats. It also seems to have two parts. The first part has 7 seats on one side and the other has one 5.
- Sam commented in TSE that he hates crates, which could have been the reason why for making him crash on Earth, stopping him from reaching Sirius and killing Mental. It's possible that either Mental or his minions broke the brakes on the crate bus to stop Sam from reaching him, or the brake really was broken.