The Terminator gets his gun from Cleveland, his pants and shirt from Peter and his motorcycle, jacket and sunglasses from Ernie, but the shoes he wears simply appear on his feet without explanation.
When Stewie opens the access panel on the Terminator, it is on the side of his head. But in an overhead shot, the panel is on the back of his head.
When Stewie and Brian decide to travel to the future, Stewie pulls out a portal gun from Rick and Morty (2013). Except Rick is adamantly against time travel. Not only is the portal gun not capable of time travel - it only travels between locations or between alternate dimensions - Rick would never add such functionality.