"Does the character time travel?"

"Is the character alien?"

"Is the character male? Is the character human?"

"Good work Rob. I was thinking the Thing too."

"Just a WAG here: Is it Korg?"

"Always felt this was one of Marvel's best Silver Age fights, so I'm looking forward to this."

"Was the character the character is similar to a mutant?"

"The IMDB tells me Bernie Koppel appeared as Siegfried in 14 episodes of Get Smart. It sounds so few! But there were 138 episodes, so that's roughly one in ten. King Moody played Starker in 7 of those episodes, for the first time in season…"

"In "Friends", Giovanni Ribisi played Phoebe's half-brother Frank Jr. However, his first appearance in the series was as an unnamed passer-by that put a condon in Phoebe's coin jar when she was performing music in the…"

"Actually, I've been looking up most of these. Hence all the hat-tips. I figured I'd find cases on long-running shows with cast-changes."

"Actually, I've been looking up most of these. I knew the Doctor Who ones except for John Levene's monster roles, and about Edd Byrnes from broad discussions."

"If we had a hundred TV trivia contests between LB, the Commander and me, I'd come in third a hundred times."

"Jon Shepodd had a one-off role in the Miller Family period of Lassie before he was cast as the first Paul Martin in its Martin Family period. George Chandler twice appeared as Chet Power during the Miller Family period and played Uncle Petrie…"

"Charlie O'Connell had two roles on Sliders before he joined the cast as Colin Mallory for the fourth season. Hat-tip: Wikipedia. In season 3 of The Andy Griffith Show Richard Keith had a one-off role before he commenced appearing as…"

"William Windon appeared as a lawyer in an episode of the first season of Murder, She Wrote and joined the show's cast as Dr Hazlitt season 2. Ron Masak had two roles on the show before he joined the cast as Sheriff Metzger season…"

"Charlie O'Connell had two roles on Sliders before he joined the cast as Colin Mallory for the fourth season. Hat-tip: Wikipedia. William Windon appeared as a lawyer in an episode of the first season of Murder, She Wrote and joined the…"