Fantastic Four Annual

An alien in combat armour arrives on Earth, and the Fantastic Four are called to investigate. The helmet removed, the alien is revealed to be the infant terrible, last seen way, way back in issue 24. His homeworld is under attack by the Skrulls, and the Fantastic Four pitch in. However, when they arrive at Elan, the Infant Terrible is revealed to be a Skrull. Reed, however, had already deduced this, and hypnotized him into trading places, allowing Reed to take out the local Skrull vying for the role of Empress. They then proceed to the power asteroid, and break in, where they hook up with the Avengers, as depicted in Avengers Annual 14. (In fact, the same pencilled pages and scripts were used for the final portions of both annuals.) The Hyperwave bomb is detonated, and all Skrulls are locked into their current forms.