These emojis convey how happy they are!

This is because the focus is mostly on the eyes, which are always pointing in one direction or another, as you can see with the characters ^, ⌒ and≧.

Tiny or no Mouths
(o^^)oヾ(^ ^ゞo(^^o)
(o^^o)♪(o⌒.⌒o)(=^・^=)
。(⌒.⌒。)( ノ^.^)ノ゚(“⌒.⌒”)
(≧.≦*)(^^)