To count as a guest star for purposes of this market, a person

• cannot be an actor who has been part of the regular cast (i.e. many appearances across many seasons);

• can be on the Wikipedia list below, up to and including season 11, unless they are part of the regular cast (when in doubt, ask);

• so, e.g. Jerry Seinfeld, Julia Louis-Dreyfus, Elizabeth Banks or Michael J. Fox would count; JB Smoove, Ted Danson or Richard Lewis would not;

• can be an actor, celebrity or other public figure, whether they play a version of themselves or a fictional role;

• must have either a Wikipedia entry or a sufficient track record on IMDb (I reserve the right to rule out B-list actors); in doubt, ask before submitting.

https://en.wikipedia.org/wiki/List_of_Curb_Your_Enthusiasm_guest_stars?wprov=sfti1