I indeed played with a slob (Salim Benali). But I tried it again and it worked with a goaled event, luckily!
Accepted party types according to game files:
<T>221796<!--SituationSimple: Situation_KegParty--></T>
<T>33294<!--SituationSimple: Situation_HouseParty--></T>
<T>16194<!--SituationSimple: Situation_DinnerParty--></T>
<T>35078<!--SituationSimple: Situation_CostumeParty--></T>
<T>35077<!--SituationSimple: Situation_BlackAndWhiteParty--></T>
<T>212048<!--GreetedNPCVisitingPlayerSituation: situation_RoommateNPC_Party--></T>
<T>31635<!--BirthdayPartySituation: situation_birthday_party--></T>
<T>197576<!--CharityBenefitPartySituation: charityBenefitPartySituation--></T>
<T>197831<!--LampoonPartySituation: lampoonPartySituation--></T>
no mention of traits or goaled events
