Scratch
Basics
These blocks add speech and thought bubbles to sprites.
There is no sound but they can bring the sprites to life.
You can use them to make two sprites have a conversation.

For "say" and "think" there are two options:
(1) Make the speech or thought last forever (or until another programming block is activated)
(2) Make the speech or thought last for a certain number of seconds.
Screen:

Two sprites on a blank backdrop
Scratch starter project: Say and think
https://scratch.mit.edu/projects/88396409/
Programming area:

Each sprite has their own set of programming blocks.

They have the "say" and "think" blocks with new text typed into the windows.

What to do:

Select a sprite (the boy or the girl) by clicking on the image under the stage area.

Click on the programming blocks to see what happens.

What to do next:

Change the text in the block windows.
Try adding extra sprites and add "say" and "think" blocks.
A starter project for exploring "say" and "think" blocks