*When Flik visits the city underneath an old caravan/trailer, we see the Pizza Planet truck parked beside it.
*The famous A113 code is imprinted on the box beside Flik when he arrives at the city.
*See this poster for The Lion King Musical?
Here it is in the city. It's in the background beside Flik's backpack.
*The city also features a Pizza Planet mega gulp cup atop the can which doubles as a bar for insects.
*P.T. Flea rides on a box which has the fictitious product name 'Casey Jr. Cookies' written on the side. This is an obvious reference to the Casey Jr. train in Dumbo (1942) which coincidentally is director John Lasseter’s favourite film. Additionally, J. Grant is a reference to Joe Grant, an animator who was one of Walt's 'Nine Old Men' and story advisor on several Pixar films before he passed away in 2005.
*During the outtakes when Flik is stood on top of a dandelion he says “To Infinity and Beyond”, which is of course Buzz Lightyear’s famous line.
*When Thumper messes up in the outtakes he says off camera “I got it JL”, another reference to director John Lasseter.
*Also in the outtakes we see Woody appear with a clapper board.