How do I reinstate the animation feature for my MacBook Pro?

If it's the usual OS X animations used when opening and closing applications, then...

 > System Preferences > Dock

controls the settings.

If you're looking at some of the other animations that are around OS X, then some details on what you're doing (that's not animated) or looking at could help folks get you to the the settings you're looking for.

This is the OS X settings, and for recent versions. If you're really using the OS 9 classic environment, this doesn't apply.

It would appear that feature of Mail.app and HTML doesn't work.

Here's an earlier discussion with a potential (add-on) solution.