S1·E13 From Here to Fraternity

The Chipmunks make up a singing telegraph service to help buy some golf clubs for Dave's Birthday. But when Theodore loses the addresses, the boys are sent on a birthday mission, for a 100 dollar bonus. Except, that when Theodore wrote the number he wrote it upside down, so the Chipmunks end up going to the wrong house and are tricked into doing some different pranks for some highschoolers who are bored.