Open Duck Mini offers an open-source route to a duck-like biped. Its README describes a miniature Disney BDX-inspired robot about 35 cm tall with its legs extended. The README calls it a work in progress and an alpha that is not very easy to build. Check the repository and its linked bill of materials before buying parts; the dated mention of a planned v2 is not confirmation of a finished version.
Walking and talking are separate problems. Reinforcement learning trains a walking policy in simulation before transfer to hardware. The README shows training in Isaac Gym with AWD, a sim-to-sim step into MuJoCo, and sim-to-real walking described as starting to work. It names a Raspberry Pi Zero 2 W for the onboard runtime and a switch from xl330 to more powerful Dynamixel xc330-M288-T leg servos. Treat these as the documented project configuration, not a validated recipe for a different body.
For a larger duck, plan stronger servos, revised structure and power, and retraining of the walking policy in simulation for the new geometry and mass. This is a design proposal, not a tested scale-up. Add optional voice chat on separate compute: microphone, a local or cloud speech/language model, and speaker. Keep model responses away from direct joint control; begin with the robot supported, protect pinch points, and disconnect the battery before mechanical work.