While Doctor Strange is active, when an Action die is used, you may use a copy of its effect. You may choose new targets for the copy.
Moon Knight: One-Man Avenger
At the beginning of the game, choose one of your (Avengers) character cards. For the remainder of the game, Moon Knight is considered to have the text of that card (including Global Abilities) instead of this text (replacing their name with his own, if applicable).
Suppose Moon Knight selects to be Doctor Strange at the beginning of the game. Then when I have both characters active, what happens when I play an action die? Let's use Investigation (Draw and roll 2 dice) for example.
A) Play Investigation, I draw and roll 2 dice. Then Doctor Strange uses a copy of Investigation, draw and roll 2 dice. Last Moon Knight uses a copy of Investigation, draw and roll 2 more dice. It ends there with a net result is drawing and rolling 6 dice.
B) Play Investigation, I draw and roll 2 dice. Then Doctor Strange and Moon Knight both use a copy of the original Investigation. Moon Knight is now able to use a copy of Doctor Strange's Investigation while Doctor Strange is able to use a copy of Moon Knight's Investigation. A loop would start until I no longer have dice to draw and roll, or I choose not to use Doctor Strange/Moon Knight's effect. It says may so the player has the choice to stop if desired.
Answer B assumes that "use a copy" in reference to an action applies the previous Ultraman ruling of synonymous wordings.