Gas giant
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope.
Monte Iberia eleuth
The Monte Iberia eleuth (Eleutherodactylus iberia) is a small eleutherodactylid frog endemic to eastern Cuba. It is the smallest living frog in the Northern Hemisphere, about in snout–vent length. It is the third-smallest frog (and tetrapod) in the world, following "Paedophryne amauensis" and the Brazilian gold frog. It was first discovered in 1993 on Mount Iberia (Holguín Province), from which it gets its name, and exists in only two small regions of Cuba. Much remains unknown about this small creature.