Wayne's World (Game Boy) by T-HQ two previously undiscovered Easter eggs and one ULTRA Easter egg.
To record this video I used previously known STAGE SKIP CHEAT.
DONUT'S SHOP EASTER (STAGE 4)
Collect all donuts except three which are located at the three round tables in this room. You'll fall down the floor and be able to collect even more donuts and other bonuses. Walk to the far right to complete the sage or just collect all extra donuts as usual.
STAGE 2 EASTER
Go to the middle of the stage, climb to upper level just above the "EXCALIBUR GUITAR". You will see an "AMPLIFIER" with "E" powerup on it. Do not take it, just walk away and jump to the "AMPLIFIER" from the right side. Now, input on pause cheat USUABALSDARDS (previously undiscovered as well), which is seems does nothing, but not this time. Now take the "E" powerup. Continue walking till the end of the stage. On the "CD BOSS", try not to defeat it, but just make it shorter, so you could jump above it. When done, just walk away further beyond the "CD BOSS" to reveal a secret room with some developer's logo: "UBC ERTW: ENGINEERS RULE THE WORLD".
STAGE 9 ULTRA EASTER
At "STAGE 9" there are "MANHOLES" on the ground, when you jump on them 7 times you will fall down to the "STEAM TUNNEL". First, open the very first "MANHOLE" and walk left. Collect one "DONUT" item and return back to the main stage. Go to the very end of the Stage, and open the "MANHOLE" right before the exit door. See the crate just under the "MANHOLE" you falling above. Jump off to the floor, then stand where the "CRATE" is. Now, input "DUALDUAL" cheat (also previously known before) to switch to the another character. Note, if you didn't take "DONUT" item you may also need to input cheat "USUALBASDARDS" instead, this will work the same. Now, walk the to the right, and you will see the secret "GARAGE" with a car with "E" on it and the same "ERTW" on the wall. This is not just an empty secret room. Enter one of the fwollowing button sequences, no need to pause the game, to reveal more Easter egg messages:
LARDASS: "ROB MCKAY IS A GREAT GUY"
BLABLABLA: "JOHAN LOVES EVIE!"
DALLAS: "MIKE HYLUNDS "WHAT AN AWESOME DUDE""
Enjoy