Knock knock. Who's there? Colin! Colin who? Colonisation!
Just kidding, colonisers don't knock before they come in.
Colonisation Knock-Knock
Explanation
Explain Bear
Listen up, buttercup. This joke is saying colonizers are rude. They just barge in and take over without asking, unlike civilized people who knock. Get it now, or do I need to draw you a picture?