There's the Partygoer (left), the freaky looking yellow guy, and there's the Partypooper, the lil' blue frowny face on the right!

The partygoers belong to 1000Dumplings, aka 1KD

Idk who created the partypoopers

I'll name the Partygoer Smiley, and the Partypooper Frowney