It's a bit too late, but for the record, if you successfully charm Morbo's summons, they will attack him and as you know, anyone who attacks him with a melee attack will get charmed... however, a bug causes this to EXTEND your own charm, i.e. his charmed melee summons will remain allied to you untill Morbo kills them (unless they fail their attacks against it repeatedly, but that's highly unlikely to happen in this timeframe).