My 1年生 JTE introduced this activity and I thought it was a really clever way to spice up textbook dialogue practice. I haven't tried it with older classes but the concept is pretty straightforward and should be applicable to any dialogue style reading you find in your English textbooks.
Essentially, students will come to the front of the class and "perform" the dialogue in a group. However, groups can get bonus points by adding new lines to the dialogue and other students can volunteer to "interpret".
Start by practicing the reading with the whole class as usual, then break students into small groups (2-4). It's okay if there are more students than roles in the dialogue. Students can opt to say lines in unison or switch back and forth.
Give students about 10 minutes to practice the dialogue in their groups. This is when they can decide who will play what role, if they want to add new lines, and try to memorize the dialogue.
After practice time is over, ask groups to volunteer to "perform" the dialogue in front of the class. This is where the role of "interpreter" comes in. Another student in the class can volunteer to stand with the group and translate lines from English to Japanese as the performers say them.
Sticker rewards are given based on how many bonus points the students added to their performance. For example:
Normal performance = 1 sticker
+1 sticker for memorization
+1 sticker for adding new dialogue
Interpreter = 2 stickers
Have as many groups perform as they like or as time allows.
New lines of dialogue don't have to be anything crazy. Some students will go above and beyond and replace dialogue answers with their original ideas, but a simple "That's nice!"/"Me too!"/"I like~" is perfectly acceptable.
My JTE and I made a cute little nametag sign for the interpreter to wear while they interpret. Totally optional but really fun for the kids!