Fans of “The Venture Bros.” who turned in to Sunday’s episode might receive an ice cream cake for their dedication. All they had to do was call a number and pretend to be one of the show’s characters.

Sunday’s episode, “The Inamorata Consequence,” saw the two governing bodies of protagonists and antagonists in the “Venture” universe, the Office of Secret Intelligence and the Guild of Calamitous Intent, coming together at the old destroyed Venture compound for a conference. With Rusty Venture (James Urbaniak) officiating the “Treaty of Tolerance Summit,” the two groups tried to renegotiate the very strict bureaucracy of how the bad guys menace the good guys — a long-running gag in “The Venture Bros.” that imagines how the world would really function if costumed villains and heroes were constantly tussling.

The summit had what seemed like a throwaway joke early on: the catering included a Carvel Fudgie the Whale cake, an actual product in the real world that people can buy. But as is often the case in “The Venture Bros.,” the cake gag turned out to be something more. Midway through the episode, an aged-looking ad played during a commercial break, offering “Venture”-themed Carvel cakes in a giveaway to fans who called a hotline.

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According to the ad, callers enter to win one of four themed ice cream cakes: one made to look like Venture clan bodyguard Brock Samson (who YouTube commenters noted is an upside-down Fudgie), one designed like the logo of Rusty’s arch-nemesis, the Mighty Monarch, or one made to look like either of the Venture brothers, Hank and Dean.

You can watch the ad in the video above.

The phone number is real, and calling it nets fans a voicemail message recorded by the Monarch (Christopher McCulloch). In the message, the Monarch instructs fans to leave their name and email address, as well as a “vivid description” of themselves eating the cake while doing an impression of their favorite “Venture Bros.” character. “A chosen few will receive further cake instructions by electric mail,” the Monarch explains.

The whole thing comes off as a big Easter egg gag, but Adult Swim verified the cake giveaway is the real deal. The YouTube video description on the giveaway further explains that entries are open through the hotline between Sept. 2 and Sept. 23. The ad and the Monarch voicemail message warn that quantities are extremely limited, so fans might want to work on the “Venture” impressions before calling.

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“The Venture Bros.” airs at midnight Sundays on Adult Swim.