Robert Downey Jr. says having a baby is like being on a ''bad date with somebody who is really small''.

The 'Avengers Assemble' star's wife Susan Levin gave birth to their son Exton three months ago and Robert revealed he has awkward, one-sided conversations with the baby, which he compared to a bad date.

He told chat show host Ellen Degeneres: ''He's smiling and talking a little bit. It's incredible.

''Well, I mean, you know. I think he is talking. I go, 'What are we doing? What's happening?' He goes [makes baby noises]. I go, 'Really?' Kind of like a bad date with somebody who is really small.''

Robert, 47 - who already has son Indio, 18, with ex-wife Deborah Falconer - recently revealed he loves being around his ''really cute'' little one, but wishes he could have spent more time with him since his birth instead of promoting his new movie around the world.

He said: ''I love being a father again, it's brilliant. Exton's really cute and I miss him a lot.''

Despite having an 18-year gap since he last welcomed a child into the world, Robert - who portrays Iron Man in the Marvel superhero movie - still employs the same methods he used when he became a dad for the first time to Indio.

He explained: ''Fatherhood doesn't seem to have changed for me. With Exton, it wasn't really different to the last time, just the same. It's great.''