Lilo & Stitch: The Series, Season 1

[Lilo and Stitch sneak into Mertle's backyard dressed as cat burglars]

Lilo:
[imitates radio static] Black Cat to Mutant Dog. Black Cat to Mutant Dog. Come in, Mutant Dog. Stitch! That's you!

Stitch:
Oh, me?

Lilo:
When I say "Black Cat", you're supposed to answer "Mutant Dog". It's cat burglar code. Black Cat to...

Stitch:
Mutant Dog.