The correct way to say it is "Mommy and I".
Here's why:
* Subject Pronouns: "I" is used when the pronoun is the subject of a verb (the one performing the action).
* Object Pronouns: "Me" is used when the pronoun is the object of a verb or preposition.
In the phrase "Mommy and me," "Mommy" is the subject, and "me" is meant to be the second subject, so you should use "I" instead.
Example:
* Incorrect: Mommy and me went to the park.
* Correct: Mommy and I went to the park.