Scene: Inside Penny’s apartment. They are laying the package down on the floor.

Sheldon: Watch your fingers. Watch your fingers. Oh God, my fingers!

Leonard: You okay?

Sheldon: No, it hurt… (looking around) Great Caesar’s Ghost, look at this place?

Leonard: So Penny’s a little messy.

Sheldon: A little messy? The Mandelbrot set of complex numbers is a little messy, this is chaos. Excuse me, explain to me an organisational system where a tray of flatware on a couch is valid. I’m just inferring that this is a couch, because the evidence suggests the coffee table’s having a tiny garage sale.

Great Caesar’s ghost

【释】"Caesar" refers to Julius Caesar, the famous Roman politician assassinated after he took complete power in the Roman republic. As for the expression "Great Caesar’s Ghost", it is a rather old expression that is a euphemism for "good God", in the days when saying "God" as an oath was considered very rude. 这里表示惊讶，“我的天哪!” (Google，WordReference.com)

【例】A: Good Mornin’ Chief

A:老大，早上好

B: Great Caesar’s Ghost! How many time must I tell you...Don’t call me "Chief"

B:见鬼了!我都跟你说了多少次了，别叫我老大!(句酷)

set of

【释】……的集合

【例】A unique set of characters that specifies computer operation .

规定计算机操作的一种特殊的字符集。

valid

【释】well grounded in logic ，合理的(有道，下同)

【例】a valid objection.

有根据的反对

garage sale

【释】现场旧货出售，宅前出售(在出售人住所进行的清宅旧货出售)(有道)

【例】They decided to have a garage sale to get rid of some unwanted stuff.(句酷)

他们打算进行一次现场旧货出售，把一些不需要的物品清除掉.