Thank you for your answers. I can see why they changed it in the film! (Great video, by the way!). But doesn't "mono" also mean "monkey"?

yes, those would be the right words. lindo would be acceptable for sure. as for "puedes ser", it is an awkward contruction. you might try "como puede ser uno" which would include the omitted/alluded "one" in "cute as can be." However, with lyrics etc. translating word for word is no good. it ends up feeling and sounding artificial. BUT if you want to keep the same context going, you can choose something like met: a boy, "lindo a morir". It's an idiomatic expression that denotes the extent of the guy-in-question's cuteness, he's "cute to death" so to speak. Hope this helps.

1. are tan and como the right words? Yes, there are right words. 2. is lindo correct for cute? Maybe, but I prefer "mono", I think that is a taste question 3. does it sound right in Spanish "puedes ser" does not seem right. Would a Spanish person talk this way? You are right, "puedes ser" in this context is wrong, because "puedes" is second singular person of indicative, and here is needed a third singular person of subjuntive. I would translate this as: "tan mono como pueda ser" or "tan mono como sea posible" I prefer this second, is not exactly the same words, but is the same meaning and is more accurate from the Spanish way to talk.

"tan lindo como puedes ser" does sound strange ¨puedes ser tan lindo¨ sounds better to me, but the meaning is not the same. That's why in the film the song changes a little in that part. This is how they did it: "La chica está loca por mi. Me miró: fue tras de mi¨... Here's the full song: https://www.youtube.com/watch?v=85y0v8u2ZTw It was a really good guess, it's just sounds weird in spanish.