Adviser Roo:

Random while playing Dice-a-roo.

 Balthazar:

Refresh at the Haunted woods.

 Boochi:

Random event

 Cave chia:

Refresh at the cave painting page 2

 Chia Clown:

Automatic Challenger

 Chiazilla:

Refresh at the Ruins of Maraqua.

 Commander Garoo:

Refresh at space station

 Count Von Roo:

When Count Von Roo bites your pet.

 Down for maintainance Pteri:

Random event

 Edna:

Complete one of Edna's quests.

 Evil sloth Clone:

Refresh at the moon of Kreludor.

 Eyrieki:

Visit the temple of 1,000 tombs in any columned door.

 Flaming Meerca:

Automatic Challenger.

 Ghost Lupe:

Visit the neohome at soup alley 131, Neopia Central.

 Giant Ghostkerchief:

Visit newspage of 31, October, 2003

 Giant Hungry Melevolent Chomby:

Refresh at the giant omlette.

 Grarrg:

Visit Tyrannian town hall.

 Greedy Kadoatie:

Get the random even when you have to pay 5,000 np to get rid of a very annoying kadoatie.

 Harry the mutant moehog:

Automatic Challenger.

 Highland Chia:

Automatic Challenger

 Inflatable Balthazar:

Automatic Challenger.

 Jelly Chia:

Visit the Jelly Chia's page at the gallery of evil.

 Kastraliss:

Refresh at the lookups of Kastraliss.

 Kasuki Lu:

Have the Kasuki Lu collectable card in your inventory and click it.

 Kauvara:

Visit Kauvara's arcticle in the Neopedia.

 Koi warrior:

Refresh in the ruins of Maraqua.

 Lab ray scientist:

Random event at lab ray.

 Lava Ghoul:

Random event.

 Mangus the torch:

Visit the volcano

 Meerca Henchman:

Refresh at trapdoor.

 Mootix warrior:

Automatic challenger

 Mr. Chuckles

Refresh at Coconut Shy

 Mummy:

Visit the mummy's information Page.

 Pant devil:

Have the pant devil steal one of your items or land on the pant devil spot on the wheel of excitement.

 Plumbeard:

Visit room 110 at the swashbuckling academy.

 Punchbag bob:

Automatic challenger.

 Punchbag sid:

Randomly appears while battling punchbag bob.

 Qualasan Mummy:

Refresh at chapter 6 of lost desert plot.

 Quiggle warlord:

Win a battle with a Quiggle as your battle pet.

 Robo Grarrl:

Automatic challenger

 Ryshu the Nimmo:

Visit Ryshu's arcticle in the Neopedia.

 Sabre-X:

Random event in Tyrannia.

 Shadow Usul:

Have the shadow usul steal one of your items as a random event.

 Sidney:

Win a level 3 or higher prize in the deserted fairground scratchcard. 

 Slug Monster:

Visit the Ruins of Maraqua while you have "slug flakes" in your inventory and click on the place where the Slug monster appears. (in the middle of the map)

 Snow monster:

Refresh in the advent calender. Other places in Terror mountain MAY work too.

 Snow faerie:

complete one of the snow faerie's quests.

 Space Faerie:

Submit a rare item code in the grundo ware house.

 Spider Grundo:

Visit the Spider Grundo's page in the gallery of evil.

 Tax beast:

have the tax beast tax you as a random event.

 Tekkitu witch doctor:

Go on a Tiki tour. (50np)

 The black Pteri:

Random event.

 The brain tree:

Complete one of the Brain tree's quest.

 The drenched:

Refresh the Maraquan weather page on a rainy gloomy day.

 Esophagor:

Complete a Esophagor quest while not on a brain tree quest.

The snowager:

Get blasted by the snowager.

 Tiki Tack man:

Visit the Tiki Tack shop

 Turmaculus:

When the Turmaculus eats your petpet.

 Vira:

Random event.

 Zafara Rogue:

Refresh at Art Centre.