"Мені було смішно вчора."

Translation: I was amused yesterday.

[aliver]

What about "I had fun yesterday"?

[Crookfingerjake]

This seems more reasonable, otherwise the sentence makes no sense out of context.

[sagitta145]

That would be Мені було весело вчора.

[JohnSherid]

"I was funny yesterday"?

[sagitta145]

That would be "Я був смішним учора" ("I was funny", as in, I made good jokes, or, I looked funny the way I behaved or was dressed, people found me funny)