My sister and I call it "no arms and legs".... you try and pick them up when they are tantrumming and they go limp and make it IMPOSSIBLE to [ick there heavy little tuschies up!!! I LOVE THAT, especially while they are having a full on screaming tantrum in public.
Screaming & fighting with each other, especially in the car. I have a 4yr old girl & a 5yr old boy. Oh yeah, & my daughters attitude, damn, girls can be a real pain in the ass!