Pearl Exclusive Pokemon

Slowpoke
Slowbro
Slowking
Misdreavus
Mismagius
Houndour
Houndoom
Stantler
Spheal
Sealeo
Walrein
Bagon
Shelgon
Salamence
Glameow
Purugly
Palkia

Diamond Exclusive Pokemon

Seal
Dewgong
Scyther
Scizor
Murkrow
Larvitar
Pupitar
Tyranitar
Poochyena
Mightyena
Aron
Larion
Aggron
Kecleon
Honchkrow
Stunky
Stuntank
Dialga

HG/SS Headbutt Guide

Shroomish: Viridian Forest

Seedot: Viridian Forest

Aipom: Azalea Town, Mt. Silver, Mt. Silver Cave Outside (Mountain), Route 28, Route 33, Route 42, Route 44, Route 45, Route 46

Caterpie: Ilex Forest (Heartgold only)

Combee: Celadon City, Cerulean City, Route 11, Route 16, Route 25, Route 5, Route 6, Route 7, Route 8, Vermilion City

Exeggcute: Cherrygrove City, Ecruteak City, Lake of Rage, National Park, New Bark Town

Heracross: Azalea Town, Celadon City, Mt. Silver, Mt. Silver Cave Outside (Mountain)

Hoothoot: Cerulean City, Cherrygrove City, Ecruteak City, Fuchsia City, Ilex Forest, Lake of Rage, National Park, New Bark Town, Pallet Town, Pewter City

Kakuna: Ilex Forest (Soulsilver only)

Ledyba: Fuchsia City, Route 12, Route 13, Route 14, Route 15, Route 18, Route 21, Viridian Forest (Soulsilver only)

Metapod: Ilex Forest (Heartgold only)

Natu: Mt. Silver, Mt. Silver Cave Outside (Mountain), Route 28

Pineco: Cerulean City, Cherrygrove City, Ecruteak City, Lake of Rage, National Park, New Bark Town, Pallet Town, Pewter City

Spearow: Azalea Town, Celadon City, Vermilion City, Route 11, Route 16, Route 33, Route 42, Route 44, Route 45, Route 46, Route 7

Spinarak: Fuchsia City, Viridian Forest, Route 12, Route 13, Route 14, Route 15, Route 18, Route 21 (Heartgold only)

Weedle: Ilex Forest (Soulsilver only)

Wurmple: Fuchsia City, Pallet Town, Pewter City, Route 1