Nintendogs Online Multiplayer: Only Local/Asynchronous Features

No. Nintendogs (DS) and Nintendogs + Cats (3DS) have no real-time online multiplayer.

Social Features (Local / Asynchronous)

• Bark Mode (DS/DSi/3DS): Local Wireless (Ad-hoc). Your dog visits another player's house automatically when systems sleep in range. Exchanges: Presents, Swaps, Contests. No direct interaction
• StreetPass (3DS): Exchanges Pet Data (Model, Name, Tricks) with passersby. Appears in "Dog Hotel" / "Out on a Walk"
• SpotPass (3DS): Receives Nintendo DLC (New Breeds, Items) via Internet automatically

What You CANNOT Do

• See friend's dog in real-time
• Play Frisbee / Walk together online
• Trade items directly (Only via Bark Mode gift wrapping)

Alternative: Nintendogs + Cats (3DS) has slightly better StreetPass integration. For true online pet sims: Animal Crossing: New Horizons (Visit islands), Pokémon (Link Trade/Battle).