expression
what on earth is this?
Colloquial exclamation expressing surprise, confusion, or disbelief at something unexpected. Often used when encountering something strange or incomprehensible.
See also: 何だこりゃ (なんだこりゃ)
冷蔵庫を開けたら、何だこれは？変なものが入っていた。
When I opened the fridge, what on earth is this? There was something weird inside.
彼の描いた絵を見て、思わず「何だこれは」と言ってしまった。
Seeing the picture he drew, I couldn't help but say, "What on earth is this?"