C−H/C−C functionalizations with methylenecyclopropanes (MCPs) were accomplished with a versatile base‐metal catalyst. A robust manganese(I) complex enabled the expedient annulation of MCPs by synthetically meaningful ketimines to deliver, upon one‐pot hydroarylation, densely substituted polycylic anilines in a step‐economical fashion. Mechanistic studies provided strong support for a facile organometallic C−H manganation, while typical cobalt, ruthenium, rhodium, and palladium catalysts were found completely ineffective. One stone, two birds: C−H/C−C activations were realized by a versatile MnI catalysis regime, thus enabling the stereoselective construction of polycyclic anilines. Mechanistic studies provided strong support for a facile C−H manganation while typical Co, Ru, Rh, and Pd catalysts were completely ineffective.