If you’re a devoted fan of The Big Bang Theory, the last 12 years have been extremely kind to you—with no less than 281 episodes of this long-running series premiering during this time. Of course, all good things must come to an end, as fans of TBBT were reminded when the final episode aired earlier this year.

If you’ve spent the last six months struggling to go on living without the Big Bang gang, we have good news for you: between December 20 and January 5, CTV Comedy Channel is hosting a Big Bang Theory marathon. This is your chance to watch every single episode, which also means it’s also your chance to catch every single cameo. Since you’ll have to squeeze some sleep in there somewhere, here are five classic cameos you should make an extra effort to experience.

William Shatner

From the beginning of its run, The Big Bang Theory was TV’s most reliable venue for Star Trek cast member cameos. While a case could be made that Leonard Nimoy and/or George Takei made the strongest impression with their episodes, a more newsworthy appearance was made by another famous Star Trek vet: William Shatner. Going into the final season, he was high on the show’s cameo wish list and he finally gave in, playing a version of himself who also happens to be a devoted Dungeons & Dragons enthusiast.

Stan Lee

While Shatner’s still going strong at 88, several of the other show’s memorable cameos were by legends who didn’t survive to see the series finale. Take Stan Lee, a prolific master of the cameo, who made fleeting appearances in movies and TV shows every day of his life—or at least that’s what it seemed like. The Big Bang Theory was no exception, with Lee leaping at the opportunity to appear in the series relatively early in its run for a cameo in Season 3's “The Excelsior Acquisition.” Decked out in a Fantastic Four bathrobe, Lee gets an unwanted house call from Sheldon and Penny, rewarding their efforts with a restraining order.
Stephen Hawking

To make it clear that landing legendary physicist Stephen Hawking was a major coup for the series—he was well known for writing extensively about the real Big Bang theory—producers went to the trouble of including his name in his first episode. In Season 5's “The Hawking Excitation,” Sheldon managed to get his own writing in the hands of the title character, even receiving a correction from the master. An unforgettable episode for all involved, this lead to six more Hawking cameos from 2012 until his death in 2018.
Carrie Fisher

Like Stan Lee, Carrie Fisher a) wore a bathrobe and b) received an unwanted visit from Sheldon in her Big Bang Theory appearance. While she chose not to get a restraining order (as far as we know), she did appear armed with a baseball bat, visibly ready to take a swing at her unwanted houseguests. Which reminds us, the real story of this cameo was the other special guest who instigated Sheldon’s prankish visit to Fisher…
James Earl Jones

Although the names Carrie Fisher and James Earl Jones have appeared together on posters for some of the biggest movies of all-time, these actors never met in person until they co-cameoed in an episode of The Big Bang Theory. As Darth Vader, Jones only contributed a voice performance to the Star Wars movies, so it’s understandable he never met Fisher on the set. But how did they never cross paths at a premiere or a franchise luncheon? In any case, when the actors finally came face-to-face, Fisher dipped into Star Wars spoiler territory by immediately calling him “dad.” The real triumph of Jones’ cameo is the way it morphs into a full-blown supporting role, as he spends time with Sheldon on a ferris wheel, in a sauna, and singing karaoke. For any future cameo candidate, this would be a tough act to follow.
CTV Comedy Channel's Big Bang Theory marathon starts December 20 and goes until January 5.