The minis would not smile for me unless they were chewing on their tooth brushes. They love them. One day I took Taggart's away from him so I could feed him and he cried and cried until I gave it back to him.
Luckily he didn't have a melt down when I took it from him but I just couldn't get a great smile from either of them.
Marshall helped me get some good smiles from them by burping. Yep, it's the truth. Sometimes you have to do what you have to do to get smiles.