Before the Courier enters Angel Cave to meet Joshua Graham, Two-Bears-High-Fiving will walk out of the cave, pump his fist in the air, and immediately walk back inside the cave. He has no special dialogue but does speak the common language of the tribals and thus will give a generic response like "Goot" or "Jah-at-tag" when spoken to.
This character is an indirect reference to the inkblot test that takes place during character creation. A common opinion among players is that the final inkblot depicts "two bears high-fiving". There is a popular mod available that changes one of the available choices to this, and the character is a direct reference to this mod.