MissingNo is invading cobblemon, with this addon through the use of commands you can get missingno and its 4 variants in cobblemon
heres a guide on how to unlock each variant:
Missingno yellow: use a thunder stone on regular missingno at level 12
Missingno Ghost: Have Lugia in your party
Missingno aerodactyl: Take 27 damage in battle
Missingno Kabutops: Get freindship 182 on your missingno