Since you said "jokes" as in more than one, here is number two and this is just too much work so I think I will rest now.

Ole and Lars go ice fishin. Ole pulls out his new thermos and Lars says to him, "Ole, whatcha got der?".

Ole says, "Well Lars, dis here's a thermos. It keeps hot tings hot, and it keeps cold tings cold."

After awhile, Lars gets curious and says, "Vell Ole, whatcha got in dat der thermos?"

Ole says, "Vell Lars, I got a popsicle, and two cups a coffee."