Although The Fantastic Four: First Steps didn’t tease their arrival in the main universe, Shakman did hint at where the MCU is taking the superheroes next. In an end-credits scene, Robert Downey Jr.’s Doctor Doom shows up and engages with Franklin Richards, the son of Sue Storm (Kirby) and Reed Richards (Pascal).

So yes, Doctor Doom does appear in First Steps. In the mid-credits scene, we jump four years into the future and see Sue Storm and her son Franklin reading together in their home in the Baxter Building.