In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.

Sentence1: Greg has always loved seeing different animals. Sentence2: He schedules a trip to his local zoo. Sentence3: At the zoo, Greg sees lions, tigers, and penguins. Sentence4: At the end of the day Greg returns home. Sentence5: Greg is very happy he took a trip to the zoo.
Tigers, Greg, Lions, Penguins