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.
Smallest organisms
The smallest land snail is "Acmella nana". Discovered in Borneo, Malaysia, and described in November 2015, it measures only 0.7 mm. The previous record was that of "Angustopila dominikae" from China, which was reported in September 2015. This snail measures 0.86 mm.