WMG / Alvin and the Chipmunks

The 1980s series takes place in the same continuity as Teenage Mutant Ninja Turtles
The Chipmunks are mutants. The last animal the boys touched before the mutagen took effect was the kindly songwriter David Seville, who had helped them off the road on which he nearly hit them. They followed him home, and the rest is history.

On the other hand, the Chipettes may have mutated the other way like Splinter. Jeanette Miller was a human, but after being exposed to toxic waste, she was turned into a chipmunk. Why else does April O'Neil's friend in Teenage Mutant Ninja Turtles look exactly like her??

Miss Miller must have some sort of shady connections to the local police department.
How else does that explain her managing to keep her driver's license, let alone managing to avoid being arrested for reckless driving?

The whole series is a result of Dave snorting too much coke.
Three foot tall talking chipmunks. Really?

The 1980s series takes place in the same continuity as Sam & Max: Freelance Police.
Six human-sized chipmunks that walk around without freaking out everyone they meet? In fact, given the seeming low population of humanoid chipmunks that we see, it's very strange no one finds them to be at all unusual- not in the least.

The Chipmunks have all gone through puberty already.
Before their voices changed, only dogs could hear them.

In the 1980s series, time travel is responsible for any continuity errors.