unwelcome guest (noun)

1. Why don't scientists trust atoms? Because they make up everything! Just like an unwelcome guest at a party!

2. During the church's annual fundraising event, an unwelcome guest managed to sneak in without anyone noticing and eat some of the donated food.

3. In the popular anime series, a ninja character disguises themselves as an unwelcome guest to infiltrate a rival clan's party.

4. The famous painting depicts a luxurious party with an unwelcome guest standing out by their mismatched outfit and awkward behavior.