I’m Commander Shepard, and this is my favourite X on Y is a snowclone phrase originating from a line of dialogue video game Mass Effect 2, developed by BioWare. Fans of the game found the phrase unintentionally funny and highly exploitable, and began using it extensively, both sarcastically and sincerely.

Commander Shepard is the player character from the popular video game Mass Effect, in which the player has the option of changing the course of the story in major and minor ways through in-game interactions with other characters. One such interaction involves getting discounts from stores on the Citadel space station by advertising for them, proclaiming via public address that a certain store is your favorite on the Citadel. The player has the option of offering this to multiple stores, creating the humorous effect that Commander Shepard has endorsed every store as his favorite.
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