Now, there's only 3 squirrels to find in this DLC, one of which I already found on the second trackHere goes, on the track 'Junkyard Funk', get to the 2nd checkpoint and ride up the pole slightly, then go backwards down it and bail to the left, where you will fly into a container and find the squirrel, then just wait for the cut scene. So yeah.
The Junkyard Funk squirrel was also the only one I found :P It's the most obvious.
Maka91Productions found them all (he's on YouTube) and the second one.... holy cow. Best Easter Egg ever. I've linked a video below for those who want to see it. BE WARNED, it is the best Easter Egg ever. +99999999999 to RedLynx for adding this.
Spoiler: Show