When　a　clamped　membrane　of　elastomer　is　subject　to　a　lateral　pressure,　it　bulges　into　a　hemispherical　balloon.　However,　for　a　clamped　membrane　of　dielectric　elastomer　(DE)　under　a　lateral　pressure　as　well　as　a　voltage　through　the　thickness,　it　may　bulge　into　a　regular　hemispherical　balloon　or　an　irregular　shape.　This　work　focuses　on　the　anomalous　bulging　behaviors　(i.e.　the　irregular　bulging　shape)　of　a　DE　balloon　under　electromechanical　coupling　loading.　The　full　set　of　the　equilibrium　configurations　of　the　DE　balloon　is　theoretically　derived　within　the　framework　of　thermodynamics,　based　on　which　we　find　that　with　the　increase　of　the　applied　voltage,　the　pressure-volume　relationship　changes　from　the　single-N　shape　for　the　case　of　purely　mechanical　loading　to　a　double-N　shape,　where　five　or　more　equilibrium　configurations　exist　including　both　regular　and　irregular　bulging　shapes.　Through　stability　analysis　we　find　that　the　anomalous　bulging　is　a　common　behavior　for　the　DE　balloon　under　electromechanical　coupling　loading　and　all　types　of　irregular　bulging　shapes　can　be　achieved　by　following　carefully　designed　loading　paths.　Besides,　the　irregular　bulging　region　usually　has　the　largest　local　strain　which　may　initiate　the　failure　of　the　DE　membrane.　Guided　by　the　theoretical　analysis,　we　conducted　experiments　on　a　DE　balloon　under　the　internal　pressure　and　electrical　actuation.　Typical　irregular　shapes　were　successfully　observed　and　the　entire　evolution　of　the　shape　changing　agrees　very　well　with　theoretical　predictions.　These　findings　enrich　understandings　of　highly　nonlinear　behaviors　for　soft　materials　under　electromechanical　coupling　loading.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.