This activity is about practicing relative pronouns, although it's not really a thorough practice of the grammar point, so you might want to look at other relative pronoun activities if you need something that involves students creating their own sentences. The fun of this activity is seeing how well the students know their classmates.
First, I quiz the JTE about a couple other teachers at the school. "I know a teacher who likes cats and doesn't like Japanese. Who is he?" You'll need to do some reconaissance first, of course! You could also use example students from another class you've done this activity in if the JTE is familiar with students in that class.
Next I pass out a paper to each student in the class. Just to be clear, I give each student a half-page - the activity is fairly short, so it can fit on half of a page. I ask each student to write their name and then write about what they do and don't like. What food do they like? What subject to they dislike? What musician do they like? They should write them in English if possible. This shouldn't take too long, but students can tend to waffle on what they want to write, so you might want to set a timer to create some time pressure.
Once the students are finished writing, I collect all of the papers. Next I mix them up a lot and hand them back to the students. I hand them back face-down and tell the students that they need to keep their paper a secret. When I hand them out, I try to confirm each paper to make sure a student didn't just get their own paper back. Students need to choose one item from the "like" row and one item from the "don't like" row and complete the sentence on the paper. Ideally this should be something interesting or surprising.
Next, I ask the students to stand up and quiz each other about whose paper they have. "I know a person who likes strawberries and doesn't like AKB48." "Is it Yumi?" If their partner answered correctly, they can sign their name under the "That's right!" section, and if their guess is incorrect, they sign under "Sorry..."
After 8 to 10 minutes or so, I tell the students to stop and hand the papers back to the original person. Sometimes it's fun to check if any student was particularly easy or difficult to guess.
You can modify the activity to only practice plural verbs by changing the sentence to something like "This student likes _______ and doesn't like _______." Remember to change it on both halves of the paper!