[Originally, I thought these two parts constituted just one episode and that the first season of Rebels had fourteen episodes (this is how it's listed on IMDb). According to the Star Wars website, however, each part of "Spark of Rebellion" is its own episode and the first season of Rebels has fifteen episodes, so in the midst of re-watching the fourth season, I went back and re-did the episode numbers and post URLs. I couldn't split this one into the two parts, though, because otherwise, everything would get pushed forward a week.]
Part I
2:06 - Commandant Aresko (to stormtroopers, referring to a merchant): "Take him away." In The Phantom Menace, Nute Gunray commands, "Take him away," to a pair of battle droids, referring to Sio Bibble [1:18:19], and in Attack of the Clone, Jango Fett says, "Take him away" to battle droids, referring to Anakin [1:42:30].
2:18 - Taskmaster Grint (to Ezra): "Move along, Loth-rat." In A New Hope, a sandtrooper says the same thing when, prompted by Obi-Wan's influence through the Force, he directs Luke into Mos Eisley: "Move along. Move along." [43:51].
5:30 - Sabine (to Ezra): "Good luck!" In The Empire Strikes Back, an unidentified Rebel pilot wishes Luke good luck [36:02] and Luke wishes Lando good luck [2:00:09], and in Return of the Jedi, Han and Lando wish each other good luck [Han to Lando at 50:33 and Lando to Han at 52:21].
5:54 - Screenshots don't do justice to the dynamics here, but this shot has the same basic composition as a shot in Return of the Jedi [59:34]. The camera pans with the rebels' speeders (Ezra, Kanan, and Zeb in this episode; Luke and Leia in the movie) and then stops to reveal two Imperial troopers already mounted on speeder bikes who take off in pursuit.
6:21 - Zeb suddenly slows his speeder bike so that the Imperial troops who were chasing him pass him, which is what Luke does in Return of the Jedi [59:47].
6:27 - Imperial trooper (after Kanan feigns giving up): "What the?" In Attack of the Clones, an alien on Coruscant makes this same exclamation as he sees Obi-Wan flying through traffic while hanging from a droid [15:08]; Han Solo says it in A New Hope after emerging from hyperspace into a meteor shower [1:03:15], and in Return of the Jedi, a scout trooper says this after being hit by Wicket [1:05:38].
Part II
0:49 - The symbol on the door in the Imperial cruiser also appears in Echo Base in The Empire Strikes Back [33:36], and these particular shots even have a similar composition:
1:05 - Ezra (to Kanan and Zeb): "It's a trap! We gotta get out of here; it's a trap!" Admiral Ackbar says, "It's a trap!" in Return of the Jedi [1:35:03], and Leia says it twice in The Empire Strikes Back [1:39:50].
1:42 - Stormtrooper (after the artificial gravity is turned off): "What the?" See above, 6:27.
4:43 - Agent Kallus (to Ezra): "You're here to be used as bait upon our return to Lothal." Obi-Wan uses the same expression in Attack of the Clones (speaking to Anakin, referring to Padmé): "You're using her as bait" [11:22].
7:56 - Ezra (after hearing that the Rebel ship has returned): "They came back! I don't believe it." The context is quite different, but Luke also says, "I don't, I don't believe it" in The Empire Strikes Back, after Yoda uses the Force to get his X-wing out of the swamp [1:13:10].
15:42 - Wilhelm scream (stormtrooper)
16:14 - Ezra (to Kallus): "I don't know where you get your delusions, buckethead; I work alone." Leia has a similar line in The Empire Strikes Back, talking to Han: "I don't know where you get your delusions, laser brain" [17:20].
19:00 - The color palette is simpler, but in Ezra's home there are a few hexagonal panels like those seen in the homestead garage in Attack of the Clones and A New Hope:
19:10 - Kanan (to Ezra): "The Force is everywhere. It surrounds us and penetrates us. It binds the galaxy together." Obi-Wan similarly describes the Force in A New Hope: "It's an energy field created by all living things. It surrounds us and penetrates us. It binds the galaxy together." [34:41].
20:35 - Obi-Wan (in a holocron recording): "And in time a new hope will emerge." This is obvious, but I'll note it anyway: "a new hope" is also the title of the first movie.