Parenting advice is no doubt as old as time itself. There is good advice, and then there are myths.
The Walt Disney Company is, in a roundabout fashion, owning up to one myth, which is that their Baby Einstein videos make babies smarter. This has been a well-known myth in scientific circles — the American Academy of Pediatrics recommends no videos of any type for children under 2. Controlled experiments are tough, since it’s hard to assign children to either watch or not watch TV (this tends to correlate with parental factors), but a quick search found a conference paper showing that toddlers have difficulty learning words presented on television, which fits with what I hear from other language development people that young children do not learn vocabulary from television (this isn’t a literature I know well — the youngest kids I study are 4 years old).
This brings up a myth about bilingualism. Many parents believe that raising a child bilingual makes them smarter. Some do this by having their children watch Spanish-language programming like Diego. This is likely a waste of time for two reasons: first, children typically do not learn a language if it makes up less than 20% of what they hear during a day. So a television program or two isn’t going to do much good (again, citing other language researchers; I didn’t see an obvious paper relating to this).
Second, though, the evidence that bilingualism makes a baby smarter is weak. The problem, again, is that controlled experiments are impossible. There is no way of randomly assigning toddlers to be bilingual or not. And bilingualism correlates with family (e.g., cultural and genetic) factors. As anyone who has spent time with a bilingual family knows, raising a child bilingual is a lot of work, and many parents don’t bother. The parents who do are, by definition, not randomly distributed.
That said, there is a good reason to raise your children bilingual, even if it doesn’t make them smarter: your children will be able to speak two languages! And that’s pretty useful.
But if you want to make smarter babies, the best option I know of is to play with them more.