The original sealbomb was a photo of penguins being photobombed by a cute seal in the corner, and it spread like wildfire throughout the interwebs. However, Sealbomber wasn't satisfied with this photobomb and continues to travel around the world, inserting his cuteness in as many photos as he can. The website that started sealbombing is sealbomber.tumblr.com, and it started about a week ago. (April 19)

Original sealbomb:

Proper sealbombs have a picture of Sealbomber peeking out from the corner. Text is placed on the image or a caption explains the image. Sometimes, the text follows the lolcat style. The effect is supposed to be humorous.

Examples:

Heidi Klum, Seal, and Seal.