Conk (voiced by John DiMaggio) was a caveman who resided in primitive Danville who later became frozen inside Danville Glacier around 29,000 years ago. He is a Cro-Magnon.
Unfrozen by Phineas and Ferb in their garage, he picked up English extremely quickly including words like "sandwiches." He was eventually mistaken by Candace to be Jeremy in his costume.
Conk appeared to be very hungry when Phineas and Ferb took him back to the garage, because he started to try and eat everything.
Conk was also very curious, and appeared to very very interested in things, like the diver helmet, which he kept banging on his head. ("Boyfriend From 27,000 B.C.")