What are the similarities between what is happening in Ukraine now and Crimea?

Only similarities are the two major players. The Crimea annexation came during nationwide demonstrations in the Ukraine against the pro-Russian President who withdrew from a EU deal favored by most Ukranians to accept a loan from Russia, leading to the Ukranian President abdicating and fleeing to Moscow. In the resulting chaos Putin sent provocateurs in to Crimea to secure its Parliament building, organized pro-Russian demonstrations by the Crimeans, and had a pro-Russian leader installed in Crimea and pushed through a referendum for annexation. Crimea's population, like the Donbas areas, tend to be more of Russian heritage and language, so it was all under the guise of self-determination by the people residing there rather than an armed invasion by military forces under a Russian flag.