there are a few lessons to be learned from Toy Story like you can have more than one favourite toy,

Learning to grow up

If I may add to this, learning how to grow up without emotionally shedding the things that you so cherished in your youth. This is best used in the final scene of Toy Story 3 but without spoiling it, I'll just say it portrays the transition perfectly.

Also from the toy's perspective, learning to accept change, loyalty to your friends and family and perseverance.

If you're going to light something, always carry a spare match. XD

If you're on a stealth mission inside a Pizza Planet, do not hide in the claw machine.