Note that conjunctions are pretty important for some of these sentences.
Materials:
Sentences (cut out)
White boards, markers, erasers (just paper is fine, too)
Leaderboard (on the blackboard)
Timer
Sentences attached. Cut them out and put on the front of the desk. Some are to combine simple sentences into one sentence, and some are to separate one complex sentence into three or more simple ones. Explain this idea with examples:
S-->C I like soccer. I play it on the weekend. --> I like playing soccer on the weekend.
C-->S Pikachu is a cute character that is loved by many people --> Pikachu is a character. He is cute. Many people love him.
Have students make groups and play janken to decide order. Distribute whiteboards, markers and erasers.
How to play:
First student comes up and memorizes as much as they can of one sentence, and goes back to their group to relay what they remember, going back and forth as much as they need to to get the whole thing across. Once they've finished getting the original sentence(s) on their whiteboard, they should either assemble the simple sentences or dismantle the complex sentence. Once they've finished they check with either the ALT or JTE (I recommend using a red marker to point things out). If they get it, they can mark a challenge as finished in their row on the leaderboard (for example: "C-->S #3"). Play for as long as you need. Advanced students could finish all challenges in about 25 minutes, but with enough sentences you could go a whole class, or if you take out the relay aspect you could make it a short warm-up.
Make sure to gauge your students' level before attempting to use this activity! I first tried with a mid-level class and it bombed pretty hard so I was reluctant to try it again, but one of my advanced classes did very well. The teacher was pleased with the activity because the simple>complex challenge helped their composition skills quite a bit. Also, I recommend adding conjunctions to the tags, since they are pretty essential for most of the sentences.