1) Show pictures and get them to repeat the words chorally and individually to check their pronunciation. Write the words on the board.
2) Next flash the pictures quickly while they shout out the name to check that they remember which is which. (which is witch
?)
3) Then instead of just repeating the word, have them say
I'm a (witch/pumpkin/bat/ghost) etc. But they have to say it in a voice suitable for that character- eg in a witchy voice when they say
I'm a witch, in "short dumpy" voice when they say
I'm a pumpkin. And get them to add gestures at the same time.
4)Then when they are used to that, get them individually to say a "neutral" sentence - eg
It's Hallowe'en tonight - but in one of the voices (their choice). The rest of the class have to listen and shout out what character they think the person is.