Joke Day
A funny activity that can be performed by the whole class is "joke day." The teacher tells the students to come to class the next day prepared to tell a joke. The only rule is that it has to be a clean joke. The teacher can also prepare a joke and get in on the game.
Stories
Everyone sits in a circle and the teacher or a student will start by telling the beginning of a story. For example, "A dog was running down the street." The next person adds a little bit more to the story such as "because he was chasing the mailman." As each person adds his part, the story becomes more entertaining and funnier.
Charades
This game is usually played with two teams and one member of each team "acts out" a particular word or phrase. You can use any categories such as "famous people", "movie titles", or make it educational and make the category something to do with what they're learning in school. Use a timer and give each a team a specific amount of time to guess.
Hot Seat
This game is played with one person sitting in a chair facing the rest of the class. The teacher comes up with a word, writes it down and shows it to the class. The group gives hints and clues to the person in the hot seat until she guesses what the word or phrase is. This can also be educational through using words and phrases learning in class. Each person gets a chance in the hot seat. This game can also be played with a timer.