Spike's Changing Spots: During the other 2 movies and the tv series, Spike has 3 spots; one large one on his back, and a smaller spot just above his left and right thigh. However, in Rugrats Go Wild, for most of the time, there's no spot above the right thigh. During "Big Bad Cat", however, when he's walking away from Siri who had just fallen into a mud pool, there's a spot above his right thigh. But in the next sequence, the spot is gone. The spot reappears when Spike tells Siri he's gonna go find his babies. And then when he asks her if she's seen them, the spot is gone.
Picture with spot: http://www.angelfire.com/dragon/ebonydramon/Withspot.jpg
Picture without spot: http://www.angelfire.com/dragon/ebonydramon/Withoutspot.jpg
Picture with spot: http://www.angelfire.com/dragon/ebonydramon/Withspot2.jpg
Picture without spot: http://www.angelfire.com/dragon/ebonydramon/Withoutspot2.jpg
Please note that Spike's spots may have changed more times than that. These are just 2 events in which they do change.