SpongeBob has worked for the Krusty Krab for at least 31 years, according to his 374 consecutive Employee of the Month awards. He is considered a kid because sponges can live to be 500 years old.
When Patrick and SpongeBob are trapped in the fishbowl in Shell City, there is one shot where the gravel in the bottom is reflected on the side, but Patrick and SpongeBob are not in the reflection.