Dog Illusion is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

This creature's power and toughness are each equal to twice the number of cards in your hand.

How it works : Dog Illusion

Original English text — Wizards of the Coast / Scryfall

No additional ruling has been published for this card.

Interactions with other cards

These cards' text mentions Dog Illusion.

Mordenkainen

+2: Draw two cards, then put a card from your hand on the bottom of your library. −2: Create a blue Dog Illusion creature token with "This token's power and toughness are each equal to twice the number of cards in your hand." −10: Exchange your hand and library, then shuffle. You get an emblem with "You have no maximum hand size."