Scratch

The "say" and "think" blocks do not give you any control over the fonts.
You can make your owh speech bubbles as an extra sprite, and send broadcast messages to make the sprite have the right costume and show itself.  Ths would give you complete control over the fonts, colors, and shape of speech bubble (but would be more work to program).

ElMikkino, your project would be better if you used the "if sprite clicked" to push the button, rather than the space bar.  Other than that, it is a pretty good example of how to get text in fonts (not using say and think).