Paula's loopy antics were the highlight of an otherwise boring "American Idol" episode -- and TMZ has learned a mid-afternoon cocktail may be to blame.

Abdul was bubbly when she left Maggiano's around 1:00 PM yesterday and had to have an assistant shut her up. Spies inside tell TMZ that Abdul was served at least one martini while in the restaurant. Must have been a stiff drink or she's a major lightweight -- "Idol" didn't go live for another four hours.