The saying is derived from a commercial advertisement for Trix cereal. Tricks, the Trix Rabbit — an anthropomorphic cartoon rabbit who finds children and wants to trick the children into giving him a bowl of cereal. He would burst with enthusiasm but he would be discovered every time; and the kids would always reprimand him with the signature phrase “Silly rabbit! Trix are for kids!” It has a slang meaning, adopted by adults to mean something like "Dont play silly games , tricks are for kids" it basically means "Be an adult"

Im not sure what the second sentence means. I am familiar with the movie but i cannot remember this sentence. Do you remember what movie scene it was used?

I just watched that movie scene and im not sure what was meant to be implied with that statement. The director , Quentin Tarantino, is a movie genius and im sure it had some type of hidden meaning. My understanding is that O-Ren Ishii complimented The Bride's sword and she knew that they were about to have a sword battle. While looking at The Bride, O Ren Ishii noticed all of the blood on her clothing and said " I hoped you saved some energy, if not you might not last 5 minutes." "But as last looks go, you could do worse" This is not a common term or slang that we use here in the US.

You are very welcome.

@Shahin Hi Shahin. can you help me on this? What does my second question mean?