I once went as Shirley Temple in a blonde curly wig, very short dress, white knee socks & mary jane type flat shoes (I stuck taps on them but not essential) - you could also carry a large lollipop (On the good ship lollipop). It was a huge party at Finsbury Town Hall and I won 3rd prize!!
Otherwise if you prefer to be a bit more glamorous you could go as Veronica Lake (blonde wig), Rita Hayworth (red wig) - or you could go as Charlie Chaplin wearing a black trouser suit, bowler hat, walking stick, moustache.