Say hi, everyone!
Step 1: Happiness
This is easily shown with the mouth. It can be in the form of a simple smile, cat smile (shown on chibi Sauwen), or a big smile with an open mouth (as seen on the instructables robot.)
Note: The cat smile can often be a symbol of cunning, like the character may be up to something suspicious since cats are stealthy creatures.
The eyes can be normally open or seemingly closed (somewhat signifying their smile is so big that their eyes squint). In Chibi Sauwen's case, her eyes resemble an upside-down u. In the instructables robot's case, his eyes resemble the >< symbols, signifying that he's shutting his eyes because he is laughing so hard. These eyes may also represent cases in nervousness or excitement, but don't forget to change the mouth!
Finally, the heart in the bubble shows love and affection towards something the character is dealing with.
Step 2: Sweatdrop
Uh oh, it looks like the instructables robot aren't allowed to have sweatdrops. It could damage the electronics inside! (Hence, the smoke cloud of doom...)
The instructables robot's eyes are x's which shows defeat or near death.
Step 3: Sadness and Innocence
Innocence is expressed by large innocent beady eyes. Again, the cat smile is shown, but this time on the instructables robot for his silly playfulness.
Step 4: Anger and Depression
The instructable robot is seen sulking alone in the corner with the back facing the audience. This drawing makes him small and sad, with a little raincloud on top of his head. He has a bubble with multiple parallel vertical lines, indicating depression. You may also use this to show horror and disgust.
Awwww... poor thing.
Step 5: Conclusion
Hope this instructable was a fun one. For more ideas, check out the wiki page on manga iconography . Happy drawing!