Is it possible to sign OpenPGP key without consent of a key owner? If yes, can unsolicited signatures be removed from a key?

For example, I have my key listed on a key server. On one day a key issued on the name of Julius Caesar signs my key. Obviously this key is a fake key and I want to remove its signature from my key can it be done? Can I block unsolicited signing of my key? Can I make signatures appear on my key only when I have validated them?

As each certification is an independent OpenPGP packet, of course it can be deleted -- OpenPGP allows so by opening the gpg --edit-key <key-id> menu and running delsig in there. An alternative would be to use gpgsplit to split up an OpenPGP key file into its individual packets, removing the offending signature and concatenating the files again.