Ah, I was finally able to figure out the "joke," as I only got the "flat" earlier as I didn't know "huhu." I had just searched for "eulenwitz," and this thing popped up a million times. I knew "uhu" but I was too tired yet to notice the extra H to figure it was a pun. I knew one of you would lead me to the answer though!
For everyone not in on it:
Was sitzt auf einem Baum und winkt? — Ein "Huhu“!
What is sitting on a tree and waving? – A “Huhu”!
Explanation: in German, “huhu” is a greeting, while “Uhu” signifies an “owl”
They're packaging is pretty distinctive as it is, but I'm a little sad they named it after such a cool animal, but then did not seem to have an owl related logo or anything other than the Adventure Glue bottle, which I don't think exists anymore.
Some of those jokes are definitely flat, but it is nice getting insight to so many languages in a fun way.
I was glad to have fun with the German lemmings like I have had fun trying French with you. Everyone is always expected to go to English to talk together, but it doesn't need to be that way every time. It would do many good to have some experience in other languages.
What is sitting in the tree and waving (hello/farewell)?
A Huhu
That's not only a play on words. Uhu is the German word for GHO. By adding the H it turns into an interjection and word that's used when people call out in greeting/to get another person's attention. At the same time it's how Germans imitate a GHO's hoot - huhu.