A granpa who is as big as a grizzly bear or some other big animal. Often used grankids of former lumberjacks. Especially between Nicholas Riker and Ben Cranston.
Nick: This is kinda crazy. You're like a big grizzly bear!
Ben: You're right. After all, I am your Grizzly Granpa!
Nick: Am I a grizzly bear cub?
Ben: You sure are!