Batman and Something

Sometimes, me and my nephew draw together. Here's one we did recently - I drew Batman and Robin, which Logan (age 4) improved with much-needed facial hair and joined up ears (apparently, I'm told, so that Batman could have an injection). He also drew the fearsome-looking thing on the left, which he assures me 'Looks like a baddie but is actually a goodie'. He didn't tell me if it had a name.