There are five instances where Ellie will whip out her joke book. In each instance they require you to do something to trigger the event and to be in a specific location as well. The first four all occur in Pittsburgh and the last one occurs in The Suburbs. Below is a video and a description of each of the five locations. If you listen to all 5 sets of jokes, you will be rewarded with the hidden gold trophy, That’s all I got

 Joke Location #1 – You will come to an area with a bus. Three enemies will come out from on top of it. You yourself will need to climb over it to continue. What you need to do is clear the area of the enemies or wait for them to pass on their own and then wait for Ellie near the bus.

 Joke Location #2 – This occurs in the big bookstore. You need to clear the entire thing and then wait up near the exit, by the makeshift camp site.

Glitch – On some rare instances, after clearing the bookstore, Ellie won’t tell her jokes. If this happens, save your game, exit and then reload that save. She should then proceed to tell the jokes. If not, try again.

 Joke Location #3 – This is just past the bookstore. You will come to a flooded street. After a cutscene where you see some guys removing a plank, turn around and keep to the right. You’ll come to a poster of a woman in a pink dress. Wait for Ellie to come to you and then initiate the optional conversation with her. After that, she’ll wander around for a couple minutes before coming to a stop and then whipping out her joke book

 Joke Location #4 – This will be in the front area of the Hotel you climb into. You need to open the safe on the first floor and take the Training Manual. In order to do that you’ll need to climb up to the second floor and make your way to the right to find the combination on an artifact (Note to Staff) that’s sitting on the floor. Once you have got that, go to the safe and take the Training Manual inside of it. When you climb back up the ladder, Ellie will meet you at the top with some jokes in hand.

 Joke Location #5 – This is in the housing area after the sewers in The Suburbs level. You need to initiate conversation at the house at the bend in the road with the warning spray painted on the side. After that, turn around and there will be a exposed kitchen on the house across the street. Enter there and hear a tale about a BBQ. From there, you’ll need to the conversation at the ice cream truck. Once that’s all complete, go to the end of the road and wait.

Select a Chapter/Guide

Chapter  2 – Quarantine Zone (note, there are none in Chapter 1)
Chapter 3 – The Outskirts
Chapter 4 – Bill’s Town
Chapter 5 – Pittsburgh
Chapter 6 – The Suburbs
Chapter 7 – Tommy’s Dam
Chapter 8 – The University
Chapter 9 – Lakeside Resort
Chapter 10 – Bus Depot
Chapter 11 & 12 – Firefly Lab and Jackson

All 37 Optional Conversations
All 5 Ellie Joke Conversations
Toolbox Locations
Shiv Doors