drinking some nearly nice homebrew
and i would think the biggest animal i could wrestle would be a yet undiscovered type of giant sea sponge 40 feet wide and 90 foot long
( chuff monkey I AM him, Sat 13 Jun 2009, 21:50, archived)

technically that's a colony,
not a single organism
( Moon Girl Technologies horrendous beanbag, Sat 13 Jun 2009, 21:51, archived)

still in the kingdom animalia
so still an animal
( chuff monkey I AM him, Sat 13 Jun 2009, 21:56, archived)

also wiki seems to think that they are generally a colony of special cells
rather than little beasties that all live together in a big sploofy blob
so nyah
( chuff monkey I AM him, Sat 13 Jun 2009, 21:59, archived)