Many SIAs lack hands and walk on all fours, negating the possibility of performing many human tasks and behavior, though a few examples are bipedal even if their species isn't naturally so. However, when required by a joke, the SIA can sometimes act like the mostly anthropomorphic Funny Animal (Scooby dressing up in a costume to aid one of Shaggy's elaborate deceptions), the semi-anthropomorphic Civilized Animal (Astro walking with his arm around George). Sometimes, the SIA can talk eloquently, but no one except maybe other SIAs hear them.
This trope is particularly associated with works by Hanna-Barbera.