I began by playing the main theme from UP and had students sing it on "la". Then we watched this video in which the theme is clearly heard and changes based on the scene shown.
As a class we discuss instruments, tempo, dynamics, and introduce Theme and Variations. We sang a song already learned and created four variations. We had already done some other things and this was the final activity on day one.
The next class I had this video ready. It is so perfect for older elementary. There will be one or two they probably don't know but have heard the music to before. I ask my students to wait until the countdown shows "3" before guessing the title (which they get so excited about shouting out!). It was hilarious! This is 10 minutes long, show as much or as little as you would like.
Small groups were created and each chose a theme to use - anything was up for grabs and Spongebob Squarepants, Row, Row, Row Your Boat, and several others showed up but many groups chose theme songs from the Movie Theme video. Everyone in the group had to agree on the theme song.
Groups were then tasked with creating four variations on their theme song and everyone had to sing.
Over the years I have collected many "Sing Like A ...." cards similar to the ones here (free pdf). I gave students the option of using these and demonstrated (and reiterated) the need for the SOUND to be different each time. We also talked about changing dynamics, tempo, etc.
Groups decided on variations and wrote them on individual white boards, then practiced these. We also added a movement component where the movement should reflect the mood of the variation.
Students decided order of performance and everyone watching responded with two thumbs up (they heard four different variations), or one thumb up (they heard some variations). It was so much fun and they were incredibly engaged and everyone was singing! Music to my ears!
Hope you give it a try and let me know how it went!