Following the confirmation of Mephisto existing in the Marvel Cinematic Universe in Agatha All Along episode 3, the showrunner explains the mention.

Agatha All Along showrunner Jac Schaeffer has finally revealed details about the show’s Mephisto connection after its third episode aired on5. Mephisto, regarded as one of the most powerful villains in Marvel,

Was that reference an inside joke or an overt wink to the arrival of a powerful Marvel villain? According to Jac Schaeffer, maybe it's both.

The following contains spoilers for Agatha All Along, Episode 3, "Through Many Miles of Tricks and Trials." The Marvel Comics demon Mephisto could soon be making an appearance in Agatha All Along. The likelihood of the character's involvement in the story increased after he was mentioned in Episode 3,