Here’s a great and exhaustive look at the jokes and references that Pixar seemingly stuffs all of their movies full of. Some of these I have noticed, but the attention to detail here is amazing. Check it out. I was particularly surprised by the Pizza Planet truck thing. Apparently the pizza truck from Toy Story appears in every Pixar feature movie produced to date. Way cool. Of course this only makes sense or is interesting to you if you have kids and have watched these things over and over. Or if you just like animated movies, which I do.
 Enjoy.
 I saw the link on Metafilter first.